Heck yeah! Paleozoology

No, not the ones from Jurassic Park (these more closely resembled Deinonychus antirrhopus, a related, but different species). That movie implanted false ideas of what velociraptors are in the minds of millions, most of whom will, sadly, never be corrected.

In actuality, velociraptors were small (about 1.5m at the hip - they would come up to about the average man's thigh), feathered dinosaurs. They were apparently fast runners, possibly able to use their feathered, wing-like forelimbs to gain speed; these specialized forelimbs may have also been used along with the long, stiff tail for balance while perched atop prey, and both of these functions may have contributed to the eventual development of flapping flight. They likely began eating prey alive, after having pounced and pinned their victim down with their powerful back limbs, which did possess a long, retractable claw on the second toe. Analysis of this claw, and examination of the "Fighting Dinosaurs" fossil indicates it was probably used to puncture and damage the throat rather than tear open the abdomen, which it was likely not sharp enough for.

Velociraptors were probably also warm-blooded. Their predatory behavior would have required a lot of energy. The presence of feathers supports this idea, as they are useful as insulation, important in species that actively thermoregulate. Mark Norell, of the American Museum of Natural History is of the opinion, and I must agree, that animals such as this are better thought of as "very unusual-looking birds."

Crinoidea is a class of echinoderms (think starfish) that, while not extinct, qualifies for inclusion in this blog by having first appeared in the fossil record in the Ordovician Period, 488-444 mya. As there are still extant members of Class Crinoidea, they can be directly observed and studied, meaning that our knowledge base regarding them is vastly improved.

Crinoids are generally composed of three major body sections: the stem, which anchors it to a substrate; the calyx, the central portion which contains its vital organs; and the arms, which are used to capture food particles and are lined with structures called cirri that move these particles to the calyx for digestion. While most extant crinoids are free-swimming and have more or less lost their stems, some deep-sea species may have stems of over 1 m in length. Like starfish and other echinoderms, crinoids exhibit pentaradial symmetry. Crinoids have no true brain, instead possessing three distinct sets of nerves, all centered in the calyx.

Belemnites were squid-like mollusks that lived from the early Jurassic Period until the late Cretaceous. Unlike squids, they possessed ten arms of equal length with sharp, curved hooks that were used for grasping prey, but no tentacles, and also had a hard internal skeleton, which is absent in modern cephalopods. Belemnite fossils are typically the remains of the rostrum, the large, bullet-shaped portion of this skeleton.

Fossils that preserve the soft parts of belemnite bodies show ink sacs, large and well-developed eyes, and powerfully muscular arms, indicating that they were incredible swimmers, just like squids.

Eurypterida, or more commonly, sea scorpions, are ancient relatives of chelicerates (spiders and scorpions) that thrived from the Ordovician to the Permian Periods 460 to 248 mya, predating the earliest fishes. They are named for the wide, wing-shaped lobes on either side of the body, which were used to propel this predator through the waters as it hunted. Eurypterids were incredibly successful, with a near global distribution.

The long spine at the end of the tail of most Eurypterids may have been used to inject venom, but there is no evidence that any members of Eurypterida were venomous. The animals also possessed one pair of compound eyes, and another set of smaller eyes called ocelli between them. The stout walking legs of some species suggest that they may have been amphibious, and may even have been the first animals to colonize land.

Meganeura is the genus of famously huge dragonfly-like insects from the Carboniferous Period, about 300 mya. These relatives of modern dragonflies could have wingspans of up to 75 cm and were named for the pronounced and well-defined network of veins on their wings (the generic name, Meganeura, means "large-nerved"). These monstrous bugs were predatory, feeding on other, smaller insects (which may still have been enormous by today's standards) and even small amphibians. Interestingly, the larvae of modern dragonflies still hunt tadpoles.

So, I thought in addition to blurbs about particular species, I'd also post now and then on some important topics related to paleozoology. This is the first one of those, about the distinction between monophyletic, paraphyletic, and polyphyletic groups.

Cladistics is the study of clades, and a clade is a group consisting of a species and all of its evolutionary descendants. A monophyletic group is one that includes a species and all of its descendants. All clades are therefore monophyletic. Since we have not been able to directly observe evolution throughout its three billion-year history however, many of the groups that have been established are not technically clades, leading to groups that are para- or polyphyletic. Systematists (scientists who study various species and their relationships to one another, essentially cladistics) strive to establish only monophyletic groups, but this is not always possible due to the extensive gaps in the fossil record.

Paraphyletic groups are formed when some, but not all, of a species' descendants are included. These groups are extremely common, and are often established when there is not enough information available to establish a proper clade. An example is reptiles, as they are traditionally defined and as most people think of them. That is, most people will say that mammals and birds are not reptiles. In reality, reptiles only constitute a monophyletic group if mammals and birds are included, as mammals descended from the mammal-like reptiles that flourished until the Cretaceous and birds are descended from dinosaurs.

Polyphyletic groups are those composed of a group of descendants, with the most recent common ancestor excluded. An example of this kind of group is warm-blooded animals. It was once thought that birds and mammals were very closely related because they shared this trait, which we now know to be the result of convergent evolution. However, trying to construct this as a legitimate phyletic group must exclude reptiles, making it polyphyletic.

Discosauriscus refers to a genus of reptiliomorphs - reptile-like amphibians - that lived in what is now Central and Western Europe during the Permian period, about 299-271 mya.

Reptiliomorphs in general are known for technically being amphibians, but exhibiting traits of both amphibians and reptiles; forming a series of "missing links" in an evolutionary chain. Such reptilian traits possessed by Discosauriscus include a sharp-toothed jaw, short limbs, and a body covered in scales (which are interestingly arranged in concentric circles). These traits likely developed in response to the drier climate of the Permian Period, which included an expansive desert covering the interior of the supercontinent Pangaea.

Bothriolepis is a genus of the heavily armored placoderm fish that flourished in the second half of the Devonian Period, 387-360 mya. Having radiated into over 100 species with a known fossil presence on all of Earth's continents, it is considered one of the most successful placoderms.

With an adult length of roughly 30 cm, these fish would have easily been hunted by others if not for their heavily armored heads, shield-like thoracic plates, and spike-shaped pectoral fins, which were adapted both for covering the fish in sediment to hide as well as launching it off of the ocean floor, where it likely fed on detritus, to swim, as the armored body made it rather heavy.

So, I've decided once a week is not frequent enough, and will be adding a second weekly post Saturdays at noon. Don't forget to reblog anything you find interesting!

Megatherium americanum, as its name suggests, is one of the largest terrestrial mammals on the fossil record. Weighing up to eight tons (about as much as an African Bull Elephant) and reaching a height of 6m (20 ft) when balanced on its hind legs, this relative of the modern tree sloth ruled the grasslands and lightly wooded areas of Central and South America when it appeared 5.3 mya.

These large animals mostly lived in groups, but would have been safe living singly, as their sheer size was an effective deterrent to most predators. Long considered an herbivore, recent analysis of the teeth and forelimb musculature of M. americanum indicates that it may have supplemented its (considerable) dietary needs with meat, possibly taking over kills of Smilodon, the sabre-toothed cat, using the massive, curved claws on its forelimbs, though this claim is still hotly debated.

Argentavis magnificens, the largest known flying bird in the history of history. A. magnificens had a wingspan of about 7 m, could be up to 2 m tall, and weighed as much as 78 kg. Its size probably prevented it from extended periods of flapping flight; it is more likely that it soared off of mountain slopes.