Photos from the Philadelphia Zoo, pt. I

9 09 2007

As promised, here are some of the better shots from yesterday’s visit to the Philadelphia Zoo. I’m sorry to say that I’m going to soon write up something about the Zoo’s shady dealings involving it’s African Elephants (visit Help Philly Zoo Elephants for a spoiler), but for now I’m going to focus on some of the better photos out of the 500+ I shot yesterday. And away we go…

I absolutely love this fountain.

Highland Cattle
While not particularly exotic, Scottish Highland Cattle are still pretty neat.

Blue Eyed Lemur
A pair of rare Blue-Eyed Lemur, Eulemur macaco flavifrons. The black one is the male, the blonde the female, and they were very excited at the prospect of a snack (the mangabey next door was getting ded fed at the time)

Giant Elephant Shrew
One of my most favorite of all mammals, the Giant Elephant Shrew (Rhynchocyon petersi).

This, by far, was the thinnest Mara (Dolichotis sp.) I think I have ever seen.

Galapagos Tortoise
The Galapagos Tortoise (Geochelone nigra) were just beginning to stir when we arrived. They weren’t nearly as randy as they had been during our last visit (I thought I had heard it all until I hear the deep tones of tortoise-lovin’)

Petunia Elephant
An African Elephant (Loxodonta africana) that we were told was named “Petunia” was also up and about. The Philly elephants will soon be moved out of their rather meager accomodations, although it might not necessarily be for the better.

Amur Tiger Cub
This little male Amur Tiger (Panthera tigris altaica) really loved his tire. He wouldn’t let any of his brothers near it without showing his annoyance.

Amur Tiger Cubs

Amur Tiger Cubs

Amur Tiger Cub

White Lion
The strangely white female lions were relaxing in the early-morning shade. I know that their condition is a regional variation, although I forget the details at the moment.

White Lions

Male Lion

White Nosed Coati
Some of my most favorite Carnivores, White-Nosed Coati (Nasua narica) were scrounging for insects and other morsels when we passed by their enclosure.

White Nosed Coati

Red Panda
And, just for Jeremy, a Red Panda (Ailurus fulgens).

We also came across the most evil-looking Caiman I had ever seen (there was no ID plaque, so I’m not sure what species it was).

Clouded Leopard
And the Clouded Leopard (Neofelis nebulosa), as ever, was asleep in it’s hammock. I have never seen this cat move a muscle in my four visits to the Philly Zoo thus far.

Amur Leopard
Just around the corner, however, was a much more active and curious cat; a male Amur Leopard (Panthera pardus orientalis). He is one of the most beautiful big cats I think I have ever seen, and it’s a shame that he’s essentially “locked up” in his enclosure, and as far as I know the zoo does not keep a female Amur Leopard to run a breeding program for this most critically endangered cat.

Amur Leopard

I still have at least 25 pictures to share, but you’ll just have to wait a little bit longer for them. Check back later tonight for more of our friend the Amur Leopard, some Giant River Otter, White-Handed Gibbons, and plenty more.

Convergence or Parallel Evolution?

6 09 2007

Many of the world’s great natural history museums devote at least one hall to creatures that no longer exist today. In the old tradition, in order to keep any young upstarts from getting any ideas about evolution, skeletons or parts of skeletons were grouped by the functions they performed, a visitor being likely to find the wing of a bat and the wing of the bird in the same display case even though the two animals extremely distantly related. Newer layouts, conversely, have largely ignored the end-function of one line or another to group animals together by homology and their shared characters, the most well-known example being the remodeled 4th Floor of the American Museum of Natural History in New York City which has attempted to arrange its fossil collections as a walk-through cladistic diagram.

Still, the generally discarded of grouping animals by their adaptations to general habitats or niches is not without it’s charms. Over and over again, evolution has produced forms that seem to converge on certain body plans, varying habitats making some traits advantageous and others a liability, helping to adapt different organisms to their local ecologies. Flight has independently evolved several times (and the ability to glide an even greater number of times), as well as adaptations to marine environments, saber-like canine teeth, immense sails along the spine, and slicing premolar teeth, although each time such familiar features seem to arise it shows that there is more than one way to solve an evolutionary problem from any given point in an organism’s natural history. Not everything can be chalked up to convergence of form in order to carry out particular functions, however. Parallel evolution, although sometimes difficult to determine, also allows relatively closely related forms to take the same evolutionary paths, showing many of the same anatomical characters even though they diverged from a common ancestor at some point in the past and occupy at least two different lines of descent. In fact, it is often these weird and wonderful creatures that are forgotten or overlooked, more people recognizing the term “saber-toothed cat” (or, loathe as I am to say it, “saber-toothed tiger”) or the genus Smilodon than the term “Nimravid” or the genus Dinictis. The following entry, therefore, will be an attempt to navigate through the somewhat “entangled bank” of evolutionary relationships among animals that appear to be shaped in similar ways by the environment but constrained by their species’ history, showing us that there is more than one way to make a saber-toothed cat.

Back into the pool: Of Ichthyosaurs, Sharks, and Cetaceans

Perhaps one of the most well-known (or at least widely cited) examples of evolutionary convergence has been that of the similar body shapes of sharks, ichthyosaurs, and cetaceans. It’s difficult to see these three distinct groups of creatures side by side and not recognize the similarities, but why are they similar in the first place? If they belong to groups that are distantly-related branches of the evolutionary “bush,” why should they have developed similar body forms?

Icthy Shark Porp
One of the most well-known examples of evolutionary convergence; (From Top to Bottom) An ichthyosaur Ophthalmosaurus icenicus, a Porpoise, and a Spiny Dogfish (Squalus acanthias)

Shark Icthy Porp
From the 1925 creationist book The Predicament of Evolution by George McReady Price.

Creationists have been quick to seize upon the idea of convergence as if it were one of evolution’s weak points. In 1926, George McCready Price wrote the following in one of the more well-known early American anti-evolution texts, The Predicament of Evolution;

For instance, we have the shark, the ichthyosaur (an extinct kind of fish-shaped reptile), and the dolphin (a true warmblooded mammal, and not a fish at all), all of which greatly resemble each other in external shape and general appearance. Each has the same long, sharp snout, the same powerful tail, the same general fishlike shape. And yet the first of these is a true fish, the second was just as true a reptile, while the third is a mam-mal, bringing forth its young alive and feeding them by milk, just as does a cow or a horse, though it lives in the sea.

Here the evolutionists have to say that this peculiar shape and general form has been evolved separately and independently in each of these three instances. Indeed, Henry Fairfield Osborn, President of the American Museum of Natural History, New York City, declares that a very similar shape and form has been independently evolved “at least twenty-four times.”—”Encyc. Brit.,” Vol. XX, p. 578…

From this large group of facts we become convinced that these many similar or identical structures, which must have been evolved quite independently (if evolved at all), make too great a draft on our credulity. At least, these hundreds of examples of “parallel evolution” greatly weaken our confidence in homology, or similarity of parts and organs, as a proof of blood relationship.

Such arguments have become traditional amongst creationist apologists, suggesting that if convergent evolution does occur then we must throw homology out the window as similar structures will only mislead us as to the true affinities of the creatures being studied. As we will later see with Cuvier’s Ptero-dactyl, this can be a danger for scientists who are unwary and wish to shoehorn creatures into existing taxonomic categories, but not for those who actually look beyond superficial appearances.

The reason why the shark, the ichthyosaur, and the porpoise should all look vaguely the same is because they live(d) in the same environment; the ocean. An organism that is suspended in a fluid that is much denser than air can be adapted in various ways to such an “alien” environment, but physics does dictate what shapes can be taken based upon life history. It is possible to be a floating filter feeder, exhibiting a round shape, but such a strategy is essentially out of the question for animals that need to move quickly and to hunt for food. What is required is not only a powerful propulsive organ to keep the organism moving forward, but also extra appendages to allow for the control of movement and a streamlined shape to reduce drag (and hence reduce energy costs for moving through the water).

One of Charles R. Knight’s renditions of an ichthyosaur.

In fact, sharks as a whole provide a good model for various forms of ichthyosaurs. While ichthyosaurs are generally presented as already being streamlined and possessing a large caudal fin with two equally long lobes, we would be loathe to forget that they too are products of evolution and many fossils show us that they were not always an Euryapsid (thank you, johannes) answer to modern-day Lamnid sharks. Early ichtyhosaurs actually had more of a “bump” towards the back of their tail rather than a full-blown caudal fin, their overall body shape and lack of a large propulsive surface keeping them from moving too quickly through the water. A similar tail type/form can be seen in many modern day sharks like the Nurse Shark, which generally live along the bottom feeding on crustaceans and inhabitants that can be sucked out of coral crevices. Being that ichthyosaurs lack gills, it is unlikely that their early representatives were bottom-dwellers, instead preferring shallow areas, which can be especially productive in terms of food.

Modification of the “tail kink” (which was at first thought to be a taphonomic feature, early reconstructions showing “amphibious” ichthyosaurs with straight tails) seen in early forms allowed for the eventual evolution of a crescent-moon shaped tail, as well as adaptations in the skull and of the limbs into fins (the addition of digits and the addition of bones in the digits being quite common in the latest forms). This more-familiar shape would allow ichthyosaurs maximum propulsion with their caudal fin (the spine going downwards instead of upwards, as in sharks) while they would be able to exert control over their motions with their pectoral fins and would be kept from rolling in the water by their dorsal fins. The evolution of large eyes and other features aside, the overall shape and basic skeletal structure of ichthyosaurs seems to be an optimal design for medium-to-large, fast-moving, oceanic predators (although mosasaurs, pliosaurs, and plesiosaurs took different evolutionary routes).

What allowed ichthyosaurs to develop an effective side-to-side motion of the tail would not work for cetaceans, however. Ichthyosaurs developed their mode of propulsion by side-to-side motions of the spine, perhaps swimming in a mode similar to eels or cat sharks at first, a common form of locomotion in modern reptiles. This sort of motion is usually accomplished on land via a sprawling gait, the limbs being held out to the sides and the animal exhibiting a bit of a side-to-side motion as it moves along.

Whether the ancestors of icthyosaurs were sprawlers (to a greater or lesser extent, predisposing them to side-to-side motions of the tail and body) or not, cetaceans evolved much more recently in evolutionary history, and developed from ancestors that carried their legs directly underneath their body. The plasticity of early archaeocetes and their artiodactyl ancestors was greatly diminished, their hip and spine structure adapted to up-and-down undulations rather than the side-to-side motion seen in the video of the salamander. This sort of constraint has not stopped mammals from becoming adapted to the water, however, and clues to the evolution of cetacean movement can be seen in living animals like Giant River Otters;

In the water, undulations of the spine accompanied with some propulsion from the limbs proves to be very effective, and it’s not hard to imagine an archaeocete like Ambulocetus, as my friend Neil so aptly described, as a “sexy otter.” Once undulation of the spine became established as a method of moving through the water, the eventual addition of a tail fluke would do for cetaceans what the crescent-shaped tail of tuna, sharks, and icthyosaurs acheived in terms of speed and power, the body being adapted towards a streamlined appearance with (again) the pectoral fins providing lift/control and the dorsal fin preventing rolling. Larger forms of whales, namely the Mysticetes or Baleen Whales, grew to immense size and gave up some of the features that seem to be convergent with sharks and the smaller ichthyosaurs (some, in fact, did acheive whale-size), but they are derived from more predatory designs and their niche as massive, far-ranging suspension feeders free them from some constrains while imposing some new ones.

Harder Ichthyosaur
A painting of leaping ichthyosaurs by Heinrich Harder (circa 1916)

Human engineering has recognized similar constraints for motion in the water and even in the air; planes and submarines most closely resemble sharks and dolphins in overall shape, the placement and size of the wings on a 747 having much the same function as the large pectoral fins of far-ranging pelagic fish like the Blue Shark. Life in the water adapted all three groups of animals towards the same shape because there does not seem to be any other way to be a fast-moving, medium-to-large sized marine predator; speed and some degree of maneuverability are paramount. Some other lines have diverged from this shape, as noted before, but the sharks, dolphins, and (I don’t think it’s too much of a stretch to say) ichthyosaurs all occupied essentially the same niche and therefore were adapted in a particular fashion.

Do not think, however, that the convergence of three lines towards one body plan gives credence to a kind of “orthogenesis” or progressive force driving evolution. There was no sort of supernatural or external force manipulating the genetic material of these groups with the shape of a dolphin or shark in mind. Rather, the environment and local ecology determined what form would be favored through time, and even though the three groups may look the same and have significant convergences, they also have many traits in common with their ancestors, allowing us to trace their evolutionary history (which is why no one is arguing that dolphins, sharks, and ichthyosaurs are closely related or form a small monophyletic grouping).

A marsupial you wouldn’t want to meet

Living members of the Carnivora (bears, cats, dogs, civets, weasels, etc.) have always caught my attention, but there was an entire group of carnivorous mammals, now extinct, that have left no living representatives. The last known member of this group was named Thylacoleo carnifex by Richard Owen, and it has some of the strangest dentition ever seen in a marsupial. Marsupial mammals are well-known in Australia, creatures like kangaroos, koalas, and wombats coming most immediately to mind out of living extant taxa. There was a much more diverse population of marsupials during the Pleistocene, however, and the “marsupial lion” was likely a formidable predator.

A skull of Thylacoleo on display at the AMNH.

In order to understand why Thylacoleo is relevant to our discussion of convergence we need to first understand what makes living placental Carnivores so special. Many carnivores, especially cats, have a rather specialized dentition, certain molars and premolars making up what is known as the “carnissal shear.” These teeth are pointed and act like scissors, easily cutting up flesh or crushing bone. The molars behind the shear are often reduced (some groups have retained their molars in order to incorporate a more generalized diet, like dogs and bears), the dental specialization perhaps being one of the keys to the success of this group. Earlier predators of now-extinct lines like Mesonychids lacked such specialized cutting teeth, and the teeth behind the canines of the large Andrewsarchus show that their oral tool-kit was a bit more blunted.

The skull of Andrewsarchus, on display at the AMNH

Thylacoleo, a carnivorous marsupial not descended from the Miacids that gave rise to living carnivores, also developed something of a “carnissal shear” but in a different way. Rather than a battery of teeth that became sharpened, one of the upper and lower premolars of Thylacoleo became elongated and blade-like, and the cleaver-like teeth helped to sharpen each other as they moved past each other when opening or closing the jaw. Thylacoleo also had a terrible bite, the attachments for the muscles that opened and shut the jaw were massive, somewhat constricting the amount of space the brain could take up, but giving Thylacoleo what was perhaps the most powerful bite forces amongst mammalian predators, especially given it’s relatively small body size (it was only about four feet long and 220 pounds).

Thylacoleo is an odd marsupial in another respect; the claw on its thumb was retractable like that of a big cat. This sort of adaptation is especially useful in keeping claws sharp, and perhaps keeping the claws sharp would allow Thylacoleo to get a good hold on its prey before going to work on it with its teeth. At this point I should probably mention that some scholars in the past have thought that Thylacoleo was an herbivore, not unlike the extant marsupial Phalangers. I will leave the response to such an argument to Richard Owen;

These eminent authors received the support, in reference to objections to my conclusions, of the (then) Curator of the Australian Museum, Sydney, Mr. GERARD KREFFT, who, in his contribution to the ‘Annals and Magazine of Natural History,’ series 3, vol. 18, 1866, p. 148, records his opinion that “the famous marsupial Lion was not much more carnivorous than the Phalangers of the present time.”

The species of carnivorous Phalanger is not named. No evidence of such by fossil specimens has reached me, nor have I found such exceptional habit of an existing species of Phalangista elsewhere noted.

As my friend Zach has noted, however, calling Thylacoleo a “marsupial lion” is a bit misleading. Even though some lion-like aspects of the skull (the results of convergence on a hypercarnivorous lifestyle, and Thylacoleo means “pouched lion”) led the anatomist Richard Owen to name the creature on the basis of such resemblances, the ways in which Thylacoleo shows its marsupial affinities are much more important. Referring to this animal as the “marsupial lion” without qualifications (as well as calling the extinct Tasmanian Tiger the “marsupial wolf”) usually confuses more than illuminates, and creationists often take the names and superficial resemblances to mean that evolution didn’t occur. Instead, they propose that God made the beginning of a “kind” of carnivorous mammal which was preserved on Noah’s Ark and gave rise to all later forms, important reproductive habits deemed to be of little consequence.

Even so, Thylacoleo carnifex and its relatives represent a branch of marsupials that became fairly specialized predators, and given the plasticity of tooth structure, it’s not hard to see how sharp premolars could be adapted into a blade to cut flesh. While it may be easy to draw connections between this animal and living carnivores, however, perhaps we should be more measured in our descriptions; both groups met the same challenges in similar ways, but the differences are far more striking and important in this example of convergence on a particular niche.

On what day were the Ptero-Bats created?

An engraving of the creature now known as Pterodactylus antiquus, the very one described by Collini.

Before there were natural history museums, there were motley assortments of organic odds and ends known as curiosity cabinets, and in the cabinet of Karl Theodor there would eventually come to be a petrified treasure. Although it was probably collected around 1767, the first known pterosaur fossil was not described until 1784, when the appointed caretaker of the collection, Cosimo Alessandro Collini, attempted to determine the nature of the strange creature that came to him from the limestone of Bavaria (the same deposits that later yeilded Archaeopteryx). Although certain that he was the remains of an animal from an earlier time, Collini was agnostic about what kind of animal he had come to possess. Years later, the famed anatomist Georges Cuvier investigated Collini’s paper and illustrations, noting that the creature was certainly a reptile. Still, the fossil would remain without a proper name until Cuvier would write a more detailed analysis in 1809, dubbing the fossil “Ptero-dactyle.”

Not everyone agreed with the analysis of Cuvier, however, especially since Cuvier did not get to see the fossil himself and had to work from the drawings in Collini’s paper. Samuel Thomas von Soemmerring, of the Bavarian Academy of Science, thought that the pterosaur was some unknown type of bat, a view that would remain entrenched in the minds of some scientists for many years. Indeed, one restoration by Edward Newmann in 1843 (and “re-drawn” for Gosse’s work Omphalos, as shown below), depicted the two known types of pterodactyl known at that time as fuzzy bats, complete with cute little ears. It is clear from the drawing that pterosaurs do not make good bats, although this didn’t stop many German paleontologists from taking such a stance through the first half of the 19th century.

Ptero bats
Newmann’s “marsupial bats”, conspicuously missing their ears, from Gosse’s Omphalos. It’s likely that Gosse recognized the reptilian nature of these Pterodactyl by the time he wrote his book, so Newmann’s work was copied minus the more mammalian aspects.

But why was there such confusion? It is likely because there is something familiar about pterosaurs that had been seen in living bats; the extension of digits to hold a membraneous wing. While the first fossil, despite wonderful preservation, did not preserve a membrane impression, it is hard to look at it and not recognize the superficially similar structure of a bat’s wing, which also carries a membrane to enable flight. In fact, birds seem a bit unusual in developing feathers for flight; many varieties of gliding and flying creatures have taken to the air (regardless of whether they engage in powered flight or glide) by the use of membranes. Indeed, gliding may often precede powered flight, and once an animal has developed a membrane that can be stretched between its limbs to glide, the extension of the digits at the point(s) of attachment can help to expand the wing size. Such changes likely occur as a result of changes in development, natural selection favoring the invasion of a new niche based upon variations that exist in a population, although in the case of pterosaurs we can no longer test to see if this is correct.

As we just saw with Thylacoleo, however, the convergences of pterosaurs and bats are rather slight, overall. While both acheived flight on membraneous wings attached to extended digits (many more in the case of bats) and have relatively compressed bodies, pterosaurs had a much greater diversity in shape and size than modern bats. Likewise, they did not elongate the rest of their fingers, suggesting that there was some situation (be it climbing or hanging on to a perch) that the pterosaurs still needed their other fingers for (although bats can climb pretty well with their thumbs, and some have even evolved suction disks). Still, it can be said that both took to the air by similar means and had to deal with similar constraints, but their evolutionary paths are far more divergent than that of the aforementioned sharks, ichthyosaurs, and cetaceans.

It doesn’t look like much of a planet-eater to me

A female Gharial at the National Zoo in Washington, D.C.

Perhaps one of the most unnecessarily confusing groups of extinct animals are the phytosaurs. Filling the niche now occupied by reptiles like the Saltwater Crocodile, the water-dwelling archosaurs have left no living descendants despite their past diversity. At first glance, the phytosaur Rutidon looks just like a modern-day Gharial, and even though it shares a common ancestor with the reptiles that now exist in tropical watery habitats all over the world, it is not otherwise related. The most prominent phytosaur feature is that their noses are over or just anterior to their eyes on their head, not at the end of their snouts. This would allow them to breathe while completely submerged, although their eyes might not have been above water when hiding in such a manner. Even beyond this feature, their jaws seem to be fairly simple, merely having a hinge at the back to open-and-close. Compare this arrangement, here represented by the giant Machaeroprosopus gregorii, with the more complex reconstruction of the true crocodilian Deinosuchus (although, admittedly, this reconstruction was heavily based upon the living Cuban Crocodile and may not be fully accurate. It still serves to show the differences between the groups, however).

Machaeroprosopus, currently on display at the AMNH

Deinosuchus reconstruction, formerly on display at the AMNH

The most notable difference are the complex bones at the back of the throat of Deinosuchus which are arranged to slide past each other as the jaw opened and closed. No such feature is seen in the giant phytosaur. Still, even after the phytosaurs died out, crocodilians did not return to the water until about the Cretaceous period, many forms being absolutely terrifying land predators that have also long been extinct. One of the early forms was Protosuchus, a small true crocodilian that represented a line that changed little during its tenure on the earth.

Reconstruction of Protosuchus

Outside of walking relatively high off the ground, Protosuchus had a foreshortened snout which was lower than its eyes, quite different from the arrangement in living crocodilians. As seen in the Dwarf Caiman photograph, below, living crocodilians have their eye sockets on the top of their head, their eyes sticking out on the surface as well as the tip of their nose when they lie in wait for prey (or just rest, for those who would like a less sensationalist tone). Protosuchus, by contrast, has eyes to the sides of the head, even facing somewhat forward, showing that it was much more well-adapted to the land than any swamp or shallow pool. Crocodilans did eventually enter the water, however, and their fossils are among the most common of any vertebrates. Some, like New Jersey’s very own Thoracosaurus, even became marine species, and a few varieties evolved crescent-shaped caudal fins on the ends of their tails to help them swim. The common belief, however, is that crocodiles have always been crocodiles, “changing little since the time of the dinosaurs,” and such generalized half-truths do little justice to crocodilians or their distant phytosaur cousins.

Dwarf Caiman

Saber-toothed Nimravid doesn’t sound quite the same…

Many museums have cases devoted to the great saber-toothed cats of epochs long gone, but it would take someone with more than just a cursory understanding of paleontology to sort out what is really being displayed. Saber-teeth, or elongated canines, have evolved many times over in the course of mammalian history, showing up in herbivores like the living Musk Deer as well as extinct groups like the gorgonopsids. Animals as different as a Musk Deer and Inostrancevia are fairly easy to tell apart, even for the non-specialist, but what about nimravids and the “true” saber-toothed cats?

A diagram of the three ideas of Nimravid/Felid evolution.

James Whitcomb Riley is purported to have once written “When I see a bird that walks like a duck and swims like a duck and quacks like a duck, I call that bird a duck.” Unfortunately, this argument is quite popular (even being utilized by the likes of prominent Intelligent Design advocate Michael Behe) despite being very superficial and even vapid. Needless to say, it doesn’t apply to our discussion of Nimravids and true felid saber-toothed cats, but in decades past the two groups were lumped together.

<img src=”Skulls” alt=”Skulls” />

So, what makes a nimravid a nimravid? They look awfully like cats, so why aren’t they included in the Family Felidae? What makes such distinctions so difficult is that those investigating the skull of Smilodon and Eusmilus would have to be relatively well-versed in scientific jargon and anatomy in order to point out the most important differences. While some nimravids (like Eusmilus) had large canines, their teeth alone are not diagnostic, and the original factors used by E.D. Cope that differentiated these animals from “true” cats were the “alisphenoid canal, postglenoid foramen, carotid, posterior lacerate, and condyloid foramina, postparietal foramina” in the skull (Hunt, 1987). The various canals and foramina listed dictate the paths of various nerves and blood vessels in the skull, and the arrangement in nimravid skulls seem to be more primitive compared with true felids. Likewise, nimravids lack a two-chambered auditory bulla, which is a rounded bit of bone associated with the ear which true cats posess.

There are a few more obvious giveaways when dealing with some nimravids, however. Nimravids equipped with long canines often have more cone-shaped canines than those of saber-toothed cats (which are flatter in cross-section), and many have bony “sheaths” extending from the lower jaw into which the massive teeth fit. Perhaps the most famous example of this kind of arrangement is the genus Barbourofelis, an animal that has actually been assigned to its own family as it is likely more closely related to true cats than nimravids (Barbourofelis was previously classified as a nimravid). Because of this (and the fact that another cat-like offshoot, the marsupial Thylacosmilus) the tooth-sheath shouldn’t be considered diagnostic of nimravids only, but it does give you a substantial clue that you’re probably not dealing with an actual saber-toothed felid.

Despite these differences, it has often been difficult to differentiate the groups (and debate still continues). The diagram above, based upon one in Robert Hunt’s 1987 paper “Evolution of the aeluroid Carnivora. Significance of auditory structure in the nimravid cat Dinictis,” offers three simplified versions of the hypotheses about the relationships of nimravids and felids. Initially it was thought that there was a progressive evolution from ancestor to descendant in a straight line, the nimravids being the direct ancestors to the saber-toothed cats. This view does not represent how evolution truly works, however, and was found to be incorrect. In its place came a view that nimravids and saber-toothed cats diverged from a common ancestor at about the same time, going off in separate directions. This is better, and is more consonant with the data, but again it suggests that the line representing the common ancestor went extinct, either in becoming nimravids or saber-toothed cats. What seems to be the case based upon current data is that the nimravids split off from a common ancestor somewhat before the saber-toothed cats, the line containing their common ancestor continuing its own evolution as both groups evolved. Such a branching pattern is not unusual, and should even be expected, especially since there are living primates like tarsiers and lemurs that represent the overall kind of animal our ancestors once were, but still quite different and undergoing their own evolution alongside our own lineage.

The skull of Thylacosmilus, the marsupial answer to the saber-toothed cat, on display at the American Museum of Natural History in New York City. Note how far back in the skull the roots of its massive canines extend.

The skull of Megantereon on display at the AMNH. It was one of the “true” saber-toothed cats.

To complicate things even further, the skull or skeleton of the marsupial Thylacosmilus is also often thrown into the mix. Although totally unrelated to nimravids or felid saber-toothed cats, the South-American Thylacosmilus converges closely on the appearance of the placental predators, although there are some important differences. As can be seen from the above photographs, the eye of Thylacosmilus is entirely enclosed by bone on the side of the head, while in many felids and nimravids the eye socket is not entirely ringed-in by bone as if someone had bored a hole in the skull (compare the skull of Thylacosmilus with that of Thylacoleo, above). Further, the teeth of Thylacosmilus have very deep roots, going back in the skull almost over the eye. Originally it was thought that the teeth faced outward, but this was based upon a distorted skull and later finds showed the true position of the long canines.


Now that we have elimated Thylacosmilus from the running as another case of marsupial convergence, we must ask why the nimravids and felid saber-toothed cats are so close to each other in appearance. While many of the instances I’ve discussed previously have been instances of convergence, be it throughout the entire body or merely certain aspects of it, the nimravid-felid connection is a wonerful example of parallel evolution. W.E. le Gros Clark provides an excellent summation of understanding the difference in his 1959 book The Antecedents of Man;

From what has already been said, it is clear that, in assessing degrees of phylogenetic affinity, it is always necessary to take into account the factors of parallelism and convergence in the evolutionary development of related or unrelated groups. These processes can lead to structural similarities, which, taken by themselves, may be misleading. The term convergence is applied to the occasion in general proportions or in the development of analogous adaptations in response to similar functional needs. But such similarities are superficial and easily distinguishable by a detailed comparative study of the animal as a whole. For example, the resemblance in general appearance, even in a number of morphological features, of the Tasmanian wolf to a dog does not obscure the fact that in fundamental details of their anatomical construction they belong to quite different mammalian groups. On the other hand, the potentialities of parallelism seem often to have been much overestimated by some anatomists, for this phenomenon has sometimes been invoked in support of extreme claims for independant evolution of groups which are almost certainly quite closely related. We can agree with G.G. Simpson that the whole basis of parallelism depends on an initial similarity of structure and the inheritance of a common potentiality for reproducing homologous mutations, and that, this being so, the initial similarity and the homology of mutations themselves imply an evolutionary relationship. Expressed in another way, it may be said that convergence increases resemblances (which are, however, no more than superficial), while parallelism does not so much increase resemblances as maintain and perpetuate (by development ‘in parallel’ so to speak) similarities which have already existed ab initio in the genetic make-up of related types. Thus, ‘closeness of parallelism tends to be proportional to closeness of affinity.’

There are a few problems with this reasoning, namely that it seems to give credence to an almost pre-determined genetic course for the lines to evolve in parallel, although le Gros Clark makes it clear in the work that he does not support in any way the notion of orthogenesis. Still, the passage makes the important distinction that in order to undergo parallel evolution groups need to be somewhat closely related and already bear similar structures, evolution preserving many of the similar traits instead of working to the same end from two disparate points. In the case of the nimravids and the felids it seems that they evolved from a common ancestor which was probably taken to carnivory. Nimravids branched off earlier, being more “primitive,” while the felids came off the same line (or a very similar one) after it had accumulated a few more evolutionary changes. Indeed, even if form seems to be static or change little, it’s hard for me to believe that designs are not slightly adapted this way or that as if the creature was an already perfect creation not influenced by changing ecological circumstances. Still, it seems that the nimravids and felids were adapted in similar ways, their ancestral lines probably possessing at least semi-retractable claws, long and sharp canines (although not long to the extreme like its descendants), a shortened face, and a developed carnissal shear. It is really not that difficult to change a civet-like creature (or in the case of our hypothetical common ancestor, a creature a bit closer to a cat) into a saber-toothed Smilodon, the changes being modifications of existing structures more than the creation of something entirely new out of nowhere. In fact, the vertebrate tetrapod skeleton has proven to be quite versatile, and most of the major bones in any vertebrate skeleton can be found to correspond with those in another vertebrate, allowing us to compare rhinos with ceratopsians, dromeosaurs with birds, cats with dogs, ichthyosaurs with cetaceans, and humans with primates.

Of constraints and convergence

I hope that is has become clear why convergence is such a strong theme in the evolution of vertebrates. At this point in the history of evolution, vertebrates have had a chance to fill nearly every niche imaginable in a large variety of habitats over millions of years, and so common themes are bound to arise. When groups return to the ocean, the environmental constraints shape them in ways peculiar to their new way of life that would not be advantageous in other situtations (i.e. being such a large aquatic animal that you’d be crushed by your own weight if you came onto land). When mammals become adapted to be predators, their dentition and morphology must be altered if they are to be successful hunters, carnivores past and present showing some suprising similarities despite being only distantly related. Even when taking to the air, laws of physics still apply, and natural selection often works through physical and chemical constraints to produce new forms.

It is of little doubt that the tetrapod design is a versatile one, retaining its overall character through the various changes that it has endured. Indeed, even when a lineage dies out and may seem gone forever, there is no law that says a similar situtation in the future will not produce forms that may be strikingly familiar, even if such organisms are not directly related to the last group that filled their new niche. Evolution has produced “endless forms most beautiful and most wonderful” and will continue to do so long after I am gone, but random mutation/natural selection do not work in isolation from the rest of the natural world. Evolution has produced so many amazing creatures precisely because ecology, physics, and chemistry have offered up both opportunities and challenges, and I only regret that I will not be able to witness the familiar and unfamiliar about what is swimming in the seas, flying in the air, or stalking the land 500 million years from now.


27 08 2007

One of the aspects I love about the American Museum of Natural History is that no matter how many times I visit, there’s always something new for me to discover, usually something I had previously overlooked. Such was the case during my last visit, as I just happened across a little white skeleton embedded in red sediments. It was the skeleton of Protosuchus.

Skeleton of Protosuchus at the AMNH.

Although it was new to me, however, the remains of the small basal crocodile aren’t fresh out of the ground at all. In 1951, Edwin Colbert and Charles Mook published the paper “The ancestral crocodilian Protosuchus” in the Bulletin of the AMNH, v. 97, although the story of the discovery of this relatively small predator go back to 1930. In that year, the paper tells us that a Navajo Indian discovered the fossil that would eventually be named Protosuchus in an area northeast of Cameron, Arizona. The find was brought to the attention of Hubert Richardson, who owned a trading post in Cameron and was a friend of the famed fossil-hunter Barnum Brown. The following year (1931), Brown visited the site and was able to collect four specimens, all within close proximity (20 feet) to each other, deciding to name the fossil archosaurs Archaeosuchus richardsoni. The fossils were sent back to the AMNH for study, and Brown later returned in 1934 to collect two more specimens from the locality, although by this time it had become known that the genus Archaeosuchus was already occupied by a fossil the famous South African paleontologist Robert Broom had named in 1905. The genus name was thus changed to Protosuchus, and the species name richardsoni remained, honoring the man who gave Brown the tip (a great tradition in paleontological nomenclature).

Part of the problem with Protosuchus, however, was that it was not properly described for nearly two decades. In 1933 Barnum Brown did issue a short communication entitled “An Ancestral Crocodile” in the American Museum Novitates no. 638 describing “Archaeosuchus” and attempting to establish the Archaeosuchidae as a new family, but the paper merely consists of a short summary and three photographs of a wonderfully preserved specimen Brown had unearthed.

Brown’s “Archaeosuchus” (=Protosuchus) from “An Ancestral Crocodile“, American Museum Novitiates no. 638.

Despite this initial release, however, Brown never followed-up with a more detailed study, which had to wait for the diagnosis of Colbert and Mook. Although the exact position of the fossil could be disputed at the time (strong cases could be made for Late Triassic or Early Jurassic, Protosuchus now being considered to be of Early Jurassic age), one thing was certain; Protosuchus was a crocodilian and a basal one at that. Although it had previously been grouped in now-defunct taxonomic wastebaskets, it was clear to the researchers that Protosuchus, if not directly ancestral to later crocodilians, at least represented the type of animal that was ancestral to later forms.

Reconstruction of Protosuchus from “The ancestral crocodilian Protosuchus” Bulletin of the AMNH v. 97, article 3. The well-preserved rows of scutes along the back are not pictured (see illustration from Brown’s paper, above).

Although there are many aspects of the skeleton of Protosuchus that link it to later crocodilians, certain aspects of its skull are quite different from modern forms. Living crocodilians typically have their orbits on the top of their skull, the skull being adapted so only the eyes and nostrils are above water when crocodilians want to see but do not want to be seen. In Protosuchus, however, the eyes are more towards the side of the skull and in a more forward position, the opening at the back of the skull also being much larger in relation to the size of the orbits than in many living crocodilians as well. Protosuchus also looks a bit snub-nosed, lacking the long grin bristling with teeth made famous by large crocodiles in Africa and Australia. Protosuchus lacks a preorbital fenestra, as well, or a large opening in the skull in front of the eye that is so commonly seen in the skulls of theropod dinosaurs, and Colbert & Mook note that such a condition is a specialization seen in crocodilians, making Protosuchus more derived from its “thecodont” ancestors.

Dwarf Caiman
A Dward Caiman at the Reptile House of the Bronx Zoo. The skull is a bit deep dorso-ventrally than other crocodilans compared to the rest of the body, but it still is useful in illustrating the transition of the eyes to the top of the head as an adaptation to a aquatic/semi-aquatic lifestyle.

As discussed in a recent post about Phytosaurs (creatures that occupied the niche crocodiles do today, only much earlier) however, crocodiles as we know them today would not show up until the Cretaceous, many of the all-too-often forgotten crocodilans and their relatives being rather fierce and terrifying terrestrial predators (see Darren Naish’s treatment of the nightmarish Sebecosuchians). As far as Protosuchus goes, however, C.E. Gow’s 2000 paper “The Skull Of Protosuchus haughtoni, An Early Jurassic Crocodyliform From Southern Africa,” the clade to which Protosuchus and its close relatives belong underwent little change from the Early Jurassic to Early Cretaceous, likely remaining terrestrial predators rather than transitioning into the water.

As is evident from this post, however, I’m no expert on crocodilian evolution, and I have a lot left to learn. Even so, there are plenty of absolutely exquisite fossils like those of Protosuchus that are often overlooked, hidden in plain sight in museum galleries. I can only imagine what might be waiting in dusty basements, forgotten storage containers, and other out-of-the-way places, as there always seem to be far more fossils to study than paleontologists to study them. In any event, while superficial in detail, this post serves as a snapshot of an interesting group of animals now long gone, but I hope to be able to build connections to it mentally as I learn more. Next stop, Postosuchus….

Alligators? In the sewers?

17 08 2007

I’m sure this is going to come as a huge shock to you all, but I was absolutely enthralled by dinosaurs as a child. The problem was, however, that the only place that they still “lived” was in my imagination, some dark corners, and maybe in a museum basement somewhere. Living crocodilians, however, were the next best thing, and one of the first movies I ever remember seeing was the John Sayles-penned 1980 horror flick Alligator, which utterly terrified and mystified me. Part of my reaction to the film probably was due to being a kid (“Why can’t alligators be living in the sewers?”), but a far greater part of my fascination was reinforced by paleontology. Even before seeing the wonderful b-film, I had come across black-and-white photos of Deinosuchus (formerly Phobosuchus) from the American Museum of Natural History, and the prospect that there were once enormous crocodilians that could swallow you hole (as in one memorable scene in an alley in Alligator) seemed very real.


Unfortunately, I don’t think I ever got to see the huge skull of Deinosuchus on display, and the skull is no longer on exhibit in the fossil halls of the AMNH. Looking up the paper describing the reconstruction the AMNH scientists had made, there seemed to be surprisingly little material from the skull of the giant crocodilian, most of the skull actually being a conjecture as to what the animal looked like in life (something like a Cuban Crocodile, Crocodylus rhombifer). This doesn’t mean that there are no giant toothy creatures in the display cases of the AMNH, however, and one of the most impressive “near-crocodile”* specimens is the skull of Machaeroprosopus gregorii.

*To the best of my knowledge no one is calling phytosaurs “near crocodiles”, but I think it’s an appropriate pop-monkier for them to help remember their overall close relationship despite their differences.

Giant Phytosaur
The gigantic (4′ 8″ long) skull of Machaeroprosopus gregorii, from Colbert et al., 1947. Studies of the phytosaurs Machaeroprosopus and Rutiodon. Bulletin of the AMNH ; v. 88, article 2

Part of the confusion surrounding phytosaurs is that they look so much like modern crocodiles even though they are not. Much like nimravids and true saber-toothed cats, phytosaurs and crocodiles share a close common ancestor, but there are some minor (but important) differences that separate the groups. Outside some features like a more primitive ankle structure, one of the sure-shot ways to tell you’ve got a phytosaur on your hands is if I has its nostrils back on the skull just above or just anterior-to the eyes, as is the case with Machaeroprosopus (and the obligate popular paleo-book inclusion, Rutidon). Although these animals seemed to have some measured success living in the semi-aquatic niches they occupied, they left no living descendants, dying out at the end of the Triassic. Crocodiles as we know them today, by contrast, would not appear until the Cretaceous, their ancestors occupying almost entirely terrestrial or marine niches.

What is interesting about the AMNH Colbert et al. paper is that it puts forth some hypotheses about the many “species” of Machaeroprosopus found in one particular area. Rather than representing various species evolving over time, it seems more likely to the authors that various stages of life of the giant phytosaur are represented, although the other specimens are not illustrated for comparison. Further, the authors contemplate some variations in the “robustness” of the skulls and prominence of perceived nasal ridges, which would seem to suggest some sort of sexual dimorphism. I’m a bit dubious about which would end up being the male or female (naturally the females are attributed the more refined or less-prominent characters), but they could be on to something there. In fact, such sexual differentiation based on visual cues would have been important, as recent research has suggested that phytosaurs (like many extinct archosaurs) could not have smelled, and therefore used, pheromones to find mates, define boundaries, etc. (Senter, 2002). After a quick search for papers, however, it seems that Machaeroprosopus has been all but forgotten, little to no resolution coming of the growth series of the Chinle Formation or possible sexually-selected characters. This lack of information, however, does leave open the door for anyone interested enough to pick up the trail, and I certainly hope that someone does.

Update: And I nearly forgot to say that this post was initially inspired by a story that Walt of the ever-wonderful Prehistoric Pulp mentioned today called “Gator” by Robert J. Sawyer. I would have much rather seen a Deinosuchus making its way through Manhattan sewers, but it’s a quick read if you’re into paleo-oriented SF. Be sure to check out some of Walt’s other recommendations, too.

Photos from Cape May, NJ

15 07 2007


Yesterday, my wife and I left at 3 AM to arrive at the most southern point/beach in New Jersey, arriving just after the sun began to rise.


And here is my lovely wife in the early morning light;


We also encountered some local wildlife before even setting foot on the beach or pathways along the dunes. Many birds rested in their large birdhouses, and a small toad sat on the bench outside the restrooms;




Once we set foot on the beach, there were already plenty of Laughing Gulls skittering about on the sand and trying to snatch some bait from early-bird fishermen;

Laughing Gull

Tracey and I also noted a strange blob bobbing about in the surf. It turned out to be a dead jellyfish;


We saw many more of the decomposing cnidarians on the beach that morning;


After taking a little snooze on the beach, we took a short walk on a path behind the dunes, watching an immature Great Blue Heron and an egret try to catch their breakfast;



Small rabbits also abounded along the shore, and we saw many over the course of the day;


Being that it was too early to head over to the docks for our whale watching tour, we stopped by the Nature Conservancy migratory bird refuge. While most of the birds were too far away or simply not present during our visit, I did spot a number of Red-Winged Blackbirds, and this particular fellow was especially robust and colorful;


This bright flower also caught our eye;


By the time was had walked the trail it was time for our cruise, although nothing much happened for the first hour or so (outside of being followed by some laughing gulls);

Laughing Gull

The whole trip did not turn out to be a wash, however, as we came across a rather large pod of Bottlenose Dolphins (15-20 individuals) feeding close to shore, right in front of one of John Wyland’s famous “Whaling Walls” (depicting a Humpback Whale, amongst other marine life);



After the overall mediocre cruise and stopping for lunch, we headed to the Cape May Zoo, where I finally got to see some live Pronghorns (previously the only ones I had seen were the stuffed ones at the AMNH);



And, of course, no zoo trip would be complete without seeing a Muntjac;



While I had seen Capybara in zoos before, I at long last got to see one swimming, as well;



As would be expected, the American Alligators were also cooling off in the water, albeit in a more stagnant pool;


The weather was rather hot, so the big cats (lion, cheetah, tiger) mostly stayed out of the sun (and therefore impossible to photograph). I did manage to get a few shots of the leopard and ocelot, however;



The animals in the African plains enclosures were a bit more active, however, including the Reticulated Giraffes and Grey’s Zebra (previously I had only seen Grevy’s Zebras);



While not as exotic, the raccoons and swift fox the zoo kept provided me with some decent shots as well;


Swift Fox

Before leaving, we also stopped into the “World of Birds,” where I encountered this strange species with yellow waddles (and showed no fear or concern that I was photographing it from so close a range);



Not long afterwards, we ate our dinner and headed for home, overall being a good day in Cape May. I also wanted to include this picture of a deer I got a few weeks ago in Pennington, NJ, where I was petsitting;


Excellent book: The Dechronization of Sam Magruder

28 06 2007

I’m not a huge sci-fi fan, but I have to say that G.G.Simpson’s novel The Dechronization of Sam Magruder is one of the most enjoyable works of fiction I’ve ever read. I’ll get to my take on who the narrator and Sam Magruder actually are and why this matters, but first I wanted to share this particular passage dealing with evolution;

It has been said by some theorists that cases like that of the crocodile, virtually unchanged for 100 million years and more, represent a failure of the evolutionary force, a blind alley, or a long senescence. As I gazed at my antagonist, it occurred to me how false this is. Here was no failure but an adaptation so successful, so perfect that once developed it has never needed to change. Is it, perhaps, not the success but the failure of adaptation that has forced evolving life onward to what we, at least, consider higher levels? The crocodile in his sluggish waters had perfectly mastered life in an unchanging environment. No challenge arose. Our ancestors lived in a more evanescent world, where what was adaptation at one time became an inadaptive burden in 100,000, 1,000,000, or 10 million years. For them, their adaptation was always a blind struggle to keep up, to face new conditions, to exploit new opportunities. Only changing races met that challenge. Of the others, those to whom chance close the adaptive avenue of change, the unlucky became extinct and the lucky, like the crocodile, found and settled into some way of life where the challenge was absent, and there they stagnated.

Indeed, crocodiles are fortunate; adaptation and evolution has perfected them to exist in a niche that does not require major changes provided that conditions don’t drastically change overnight. Even before there were actual crocodiles, there were tetrapods essentially filling the same niche of aquatic ambush predator, and for one reason or another crocodiles beat them all out, so well-adapted to their role in the ecosystem that there hasn’t been much need for big-time evolutionary change. If there was anything like a communal memory of crocodiles, there wouldn’t be a memory of a time when there was not water to conceal themselves in, and they have been preying upon the various creatures that have visited the water’s edge the whole time. While there was once a greater diversity of crocodiles in type and habit, they have dominated their niche for so long that there is seemingly nothing they cannot handle.

This passage also speaks to what wrote in popular works like The Meaning of Evolution, in which he refutes the idea that life has some sort of vital force pushing it forward to be constantly evolving (or the idea that species, like individuals, had lifespans of birth, growth, and “senescence”), nor does evolution strive toward one perfect, unchangeable end (although crocodiles probably fooled many in this regard). While crocodiles will continue to change little by little through time, I can’t think of a reason why they should not continue to persist much as they are now for many millions of years to come.

As for the book itself, I feel that our protagonist Sam Magruder and the narrator are dual-voices of G.G. Simpson. Magruder, a scientist who is utterly lonely and stuck in a world where he feels he cannot make any lasting contribution to science, is the most powerful voice in the story, but I feel the narrator tells us quite about Simpson as well. Magruder’s story is told via 8 stone tablets that Magruder inscribed and buried, but not all the content of the slabs is shared with the reader; the academics who are disseminating the information have edited it, inserting lengthy footnotes, snide remarks, and editing what they deem to be distasteful. One such example is Magruder’s discussion of his sexual frustration, no female of his species existing for more than 65 million years into the future, but the editors decide this discussion is too frank and omit it from the public’s copy. Likewise, the narrator makes mention of, but omits, various footnotes of academics apologizing for Magruder’s behavior (such as using a colloquialism, which is apparently unbecoming of a scientist) and his ignorance of a topic (such as when sauropods became extinct in North America). These were Simpson’s little jabs at academia, perhaps venting his own frustration at fellow scientists who lacked imagination or developed a “holier-than-thou” attitude over the years.

While I did not know this about Simpson, the afterword by Stephen Jay Gould makes it clear that Simpson was a very lonely man despite his accomplishment. This was not for lack of company, but Simpson wanted so much to contribute something lasting to paleontology that he could seemingly could not bear much criticism or brown-nosing (which was worse), and the book makes it apparent that he was worried he would be forgotten. While Magruder buried his slabs, never knowing whether someone would find them (he’d be dead for at least 65 million years when they did), Simpson seemingly buried this bit of fiction, which did not come to light after his death. At the end of his life, perhaps Simpson felt like Magruder; contributing much to our understanding, but isolated from anyone who would study his work in the years to come, isolated from satisfaction and afraid that his work would be left to collect dust on a shelf somewhere. What gratification he might have gotten from people like me who are still impressed by his work, I don’t know, but it seems that intellectually Simpson felt he was stuck in the Cretaceous, never knowing what would become of the messages he left to future generations.

If you enjoy science fiction at all, and especially if you like tales about dinosaurs, I highly recommend this book; it can be read cover-to-cover in less than an evening and gives us a very personal look at one of the greatest paleontologists ever to have lived. Immediately after I closed Simpson’s book, I picked up Sapolsky’s A Primate’s Memoir, and it only furthered my enjoyment for the evening. I have absolutely loved the first 60 pages of Sapolsky’s book, and I can’t wait to get to the rest of it; it is another must-read if you’re looking for good books this summer.

Action-Packed Saturday, Pt. 2

2 06 2007

After returning home from the farmer’s market, my wife and I decided to take a trip up to Essex County to visit the Turtle Back Zoo. I visited the zoo often as a child, and at one point a lack of funding was going to cause it to close. Most of the animals at the zoo, however, were old and had no place to go if the zoo closed, so contributions came in and the zoo has been largely renovated (and is still in the process of being updated). Here are some pictures I took of the various local and exotic fauna I came across at the zoo today.


Like many other local zoos, Turtle Back had a Muntjac. I couldn’t spot the characteristic fangs on this one, and he seemed more interested in taking a nap than posing for me.


The zoos kangaroos were taking a break from the heat as well (it broke 90 degrees F today).

Red Panda

The newest addition to the zoo is a Red Panda, which decided that it would rather stay inside where it was air conditioned than come outside.


The official Kean University mascots, two cougars, also decided they would rather not deal with the heat and attempted to take a cat nap, although screaming children don’t make it easy to do so.

Black Bear

Jelly and Jam, the zoo’s Black Bears, didn’t seem to mind the heat as much though, and decided to come down close to the glass to browse some clover.


Speaking of local wildlife, I discovered some unattended eggs beneath a bush at the park. I assume they belong to a Canada Goose, although I can’t be sure. Whatever they were, I don’t think they’ll last long; they seem to just be sitting randomly without attention, so if the environment didn’t get them some lucky raccoon will tonight.


Chipmunks also darted around the zoo, a welcome change from the fat gray squirrels I’m used to around here.


PSE&G helped to renovate the alligator exhibit as well, allowing me to get much closer to a water-level shot than usual.


The above elk had an itch he had some trouble getting at.


Unfortunately the cage prevented me from getting a better shot, but I couldn’t pass up taking a picture of this sleepy porcupine (soon to get a larger enclosure in a wildlife of New Jersey exhibit).

Poison Frog

The zoo’s new Reptile House is also a huge improvement over the old concrete and iron structure, although they made some mistakes with their educational plaques that I’ll have to talk to them about.


Given the popularity of penguins these days, it was of little surprise that the zoo had a few Jackass Penguins as well (usually called “African Penguins” by zoos that don’t want children repeating the dreaded j-word all day). I really hope that the film “Surf’s Up” finally kills the recent penguin obsession; I can’t take any more bad CGI films featuring the flightless birds.


My favorite part of the day, however, was getting to see the wolves. I remember seeing some at the zoo many years ago, but the exhibit has since been renovated and is inhabited by at least 3 white wolves.


And of course, no day would be complete without a picture of myself sitting on a (searing hot) metal replica of a Komodo Dragon.



21 05 2007

Sometimes in life, expectations are not always met. Growing up I used to pore over dozens of books depicting old photographs from the American Museum of Natural History, making a mental inventory of all the fossil marvels I had to see. Outside of the dinosaurs (some of which still look very much like they did when Henry Fairfield Osborn was at the museum), I absolutely had to see the enormous reconstructed maw of Carcharodon megalodon and the massive skull of the crocodile Deinosuchus. Perhaps I did see them, but unfortunately all I recall from my early visits were the trip to the fossil halls in a cramped elevator, a museum logo featuring a human skeleton next to the skeleton of a horse, and the immensity of the “Brontosaurus” skeleton in the dim light of the dinosaur halls. Returning many years later, I made sure to take my time through the Hall of Vertebrate Origins, leaving no cladistic nook left unexplored, but alas, the massive C. megalodon jaws had been properly downsized and Deinosuchus was nowhere to be found.

All is not lost, however, as the AMNH has kindly allowed the public access to old museum documents by the likes of Barnum Brown, G.G. Simpson, Edwin Colbert, Henry Fairfield Osborn, and many others, and one 1954 publication allows me a look at the giant crocodilian I never had a chance to meet in person. Entitled “A Gigantic Crocodile from the Upper Cretaceous Beds of Texas” (by Edwin Colbert and Roland Bird from the November 12, 1954 edition of American Museum Novitiates), the paper describes a “new species” dubbed Phobosuchus riograndensis. We now know that the genus Phobosuchus riograndensis = Deinosuchus riograndensis (the type species for the genus is Deinosuchus hatcheri), and so the paper serves our interests here just fine.

The restored skull of Deinosuchus from the Colbert/Bird paper. Note the darker areas, which are the actual fossil material used in the reconstruction.

While the reconstructed skull is impressive in and of itself, it becomes even moreso when we can see its size relative to some AMNH scientists;

Deinosuchus and scientists
The restored skull of Deinosuchus, featuring (left to right) B. Brown, R. T. Bird and E. M. Schlaikjer [ref: “How the ‘terror crocodile’ grew so big” by Erickson and Brochu, Nature 398, 205-206 (18 March 1999)]

Given that a complete (or reasonably complete) skeleton of Deinosuchus has yet to be found, we can only estimate how large it was from the material at hand, likely 10-12 meters long when fully grown. But how did they get so big? It’s not easy to attain such large sizes, and it’s important to know whether huge crocodilians followed a growth curve similar to that of their living relatives or were instead fast-growing like some dinosaurs. According to this 1999 Nature correspondance by Erickson and Brochu [“How the ‘terror crocodile’ grew so big” Nature 398, 205-206 (18 March 1999)], it appears that Deinosuchus followed the standard grow-throughout-life pattern exhibited in its modern relatives, perhaps taking upwards of 35 years to fully attain the monstrous sizes we’re familiar with. Given that many extant crocodilians do not live long enough to reach maximum size, perhaps the largest individuals would be more rare than smaller ones, although I am not familiar enough with what has been recovered from these animals to prove or disprove such an idea. While I’m on the subject, of course, Darren Naish has a great post (just posted yesterday, as a matter of fact) involving giant crocodylians, so be sure check his writing out as well.

As for the fossil material discussed in the Colbert/Bird paper, here is what was recovered;

TYPE: A.M.N.H. No. 3073. Almost complete premaxillae and part of a right maxilla, portions of left articular, angular, and surangular, right and left dentaries and right and left splenials; one dorsal vertebra, probably the twelfth vertebra of the presacral series; right scapula, possible portion of a right ilium; scutes and other fragments.

For an animal Colbert and Bird estimated to be up to 50 feet long (6 feet of which being skull), not very much was left over. The reconstructed skull itself belies this, the very front of the jaws and the very back of the lower jaw making up most of the skull material, the skull as a whole being based upon the notoriously bad-tempered Cuban crocodile ( Colbert and Bird did argue, however, that their fragmentary crocodilian could be even longer than 50 feet in length because they the cuban crocodile had a more blunt snout, and if they had based the reconstruction on the Saltwater Crocodile (Crocodylus porosus) and American Crocodile (Crocodylus acutus) (which have comparatively longer snouts), the size estimate for their specimen would increase further.

It would be wonderful if I could now go on to describe Deinosuchus as we now know it, but (outside of a decrease in size) it doesn’t seem to be very different from the way it is depicted in the Colbert/Bird paper; as the Cretaceous equivalent of the modern-day alligator. Perhaps someday some more skeletal material will help us further flesh out this animal, but the lack of material hasn’t stopped it from becoming a “fan favorite” of paleontology; it often shows up along dinosaurs in model sets, books, and television shows. A more complete crocodilian is the famous Sarcosuchus imperator (and if you haven’t already seen it, check out National Geographic’s documentary SuperCroc),but hopefully more fossils from other giant crocodilians will be discovered so that some comparisons can be made among the giants.

While today New Jersey is usually free of alligators and crocodiles (I say usually because every now and then a release “pet” shows up), this was not always the case. Just in the past year, one of the most well-preserved Thoracosaurus neocesariensis skeletons was extracted from the green marl (stuff gets everywhere, let me tell you) of the Inversand pit in Gloucster County, New Jersey, by Drexel University students and Dr. William Gallagher of the State Museum in Trenton. You can have a look at the recovered material via Drexel’s website here, read a Philadelphia Enquirer article about the discovery here, see an early artistic depiction by Cope at the HMNH, or see a more recent depiction by Dan Varner at Oceans of Kansas.

When I was at the pit last fall, I found a croc scute, but there are several species of crocodilian known from the pit and I could not discern to which it belonged to. I also checked out the location from which Dr. Gallagher found the Drexel Thoracosaurus, but there didn’t seem to be any lingering fossils either, so I focused on trying to extract some bone from a spot that was bearing well in the Main Fossiliferous Layer. The bone was beige on top, dark brown in the middle, but came out only in fragments and I could not tell what I had found. Hopefully when I return on Wednesday I’ll be in luck, and you can expect a post all about what I find on Wednesday.

Photos from the National Zoo; Pandas, Wolves, Gharials, and More!

15 04 2007

Looking back, Saturday seems like a dream. I’m sure part of that is due to the fact that I only slept 2 and 1/2 hours before getting up at 2 AM to drive to the National Zoo in Washington D.C. and spend the day with my wife and her parents. Lack of sleep aside, never have I been to a zoo with such wide species diversity, and while I still consider the Bronx Zoo to be the best I’ve ever been to, I was absolutely amazed by many of the residents of the National Zoo.

My wife and I arrived at 6:30 AM, hoping to see most of the animals in the zoo while they were still active. Unfortunately, most of the animals don’t make an appearance until later in the morning and the various houses didn’t open until 8:30 and 10:00 AM, so other than the occassional jogger there wasn’t much to see. Up in a tree, however, were two Red Pandas sleeping in, and here’s one of them in the early-morning light;

Red Pandas

A Mara, in contrast to the sleeping Red Pandas, was up and about;


Around the time that my in-laws arrived more of the animals were out on display, although before proceeding my wife wanted a picture of us together next to a statue of a sloth bear. Here it is, both of us looking rather unsettled because the sun was in our eyes and we were trying to communicate how to work my camera;


One of my most favorite animals from the zoo was the Maned Wolf, although unfortunately their enclosure didn’t allow me to photograph them without a doghouse or chain fence in the background;

Maned Wolf

The miniscule Tammar Wallabies were also a highlight. Despite my appreciation for wildlife, every time I see them something in my head goes “Aww, whosanitsybitsy then?”

Tammar Wallaby

We also saw a rather old Spectacled Bear, and for some reason this particular one reminded me of Jeremy Irons. In any case, I have never seen one with an overall blond face (normally they have blond lines/patches that make them appear “spectacled”);

Spectacled Bear

I also finally got to see a Caracal in the flesh, although this was one angry cat. Frustrated that it couldn’t visit it’s other enclosure or get the birds on the outside, it wasn’t too happy when I stooped down to take its picture;


Several cheetahs were also on display, a male desperately seeking the affection of this young female (although they were separated by a fence);


I also got to see two 10-month old Bengal Tigers at the zoo, although their enclosure wasn’t exactly condusive to good photography. Here’s one of them after making an attempt to snag a bird that entered the enclosure;

Young Tiger

Speaking of young animals, two young sea lions were playing “king of the rock” in their enclosure;

Sea Lions

Two young otter brothers were also a bit scrappy, chasing each other about their enclosure and taking dirt/pine needle baths;


Other small mammals were also active during our visit, including a Banded Mongoose and some Meerkats;



Some of the local fauna proved to be just as interesting as the exotics; we spotted two white-tailed deer in the zoo as well as this small bird that had collected a flamingo feather for its nest;


I also finally obtained a photograph of one of my favorite animals, the Giant Elephant Shrew;

Elephant Shrew

While I am absolutely enthralled by mammals, I was also overjoyed to see a male and female Gharial up close in the Reptile House. Here’s the female, just before slipping into the water to join the male;


The Great Ape House also provided for some good photographic opportunities, especially some young gorillas and an oranguatan that used some cardboard as a sun hat. In fact, many of the orangs at the zoo seemed to like cardboard as a hat, blanket, etc., which I had never seen before.



Speaking of primates, this small tree shrew in the Small Mammal House slowed down long enough for me to get a good picture of it. Just seeing how it handled its food and used its hands left no doubt in my mind that primates are derived from such creatures;

Tree Shrew

I also encountered an animal I had never heard of before; the African Pygmy Falcon.

Pygmy Falcon

A Mouse Deer also made a brief appearance during our visit;

Mouse Deer

But what about the Giant Pandas? Well I was able to shoulder my way through the crowd of photographers and snag plenty of pictures of the young panda residing at the zoo;

Panda Sit

Panda Log

Panda Tree


While the young panda was certainly cute and very entertaining (i.e. watching a panda scale a tree for a good scratch), my most favorite moment from Saturday involved a female Mexican Wolf (a subspecies of Grey Wolf). When I arrived at the enclosure the three females were pacing back and forth near the back of their enclosure, stopping every now and then to look at my wife and I. There was no way I was going to get a good picture, but I discovered the cage was connected to another one the wolves could access, and after waiting a moment one of them came over to the front for a drink. After lapping up some water she took a long look at me and rejoined her pack, and here’s my favorite picture that resulted from my stroke of luck;


While the 4 hour drive each way wasn’t very fun, I did highly enjoy myself at the zoo and hope to return soon. Even so, I would love to see these animals in the wild someday. While I certainly have some ok pictures, there’s not much of a story to them; “I walked by the enclosure and the wolf looked at me,” isn’t an experience that’s earned. Granted, in the wild I would get nowhere near as close to these animals nor be able to get them to “pose” for me, but I would much rather catch a fleeting glimpse of a wolf or jaguar than know they only exist in zoos and memories.

Photo of the Day: Dwarf Caiman

24 03 2007

I love getting water-level shots of crocodilians; here’s one of a dwarf caiman at the Bronx Zoo.

Dearf Caiman

Although it’s neat to see all the different snakes and turtles, I’ve always been a little ambivalent about Reptile Houses in general. There typically isn’t much space, so lots of snakes and lizards and caimans are cramped into small displays. Granted, some things are content just to sit under their heat lamp and not do very much and during the winter the animals have to be inside, but I wish there was a way to give them a bit more space.