Weekly Spotlight: Pantylus

14 02 2010

(NOTE: I must once again present the fact that, regardless of what WordPress says on the matter, this article was in fact written and posted on Saturday!)

Good tidings and well-wishes!

People tend to be remarkably unimaginative when it comes to defining what makes something an animal. Although most individuals grudgingly accept the fact that cuttlefish, spiders, and tapeworms are indeed animals, nearly every lay person with whom I’ve conversed on the subject will readily concede that such beasts aren’t amongst the first organisms that come to mind when asked to envision an ‘animal’. The reasoning behind this curious tendency is relatively simple, if glaringly illogical: creatures such as birds, dogs, and toads share far more obvious anatomical similarities with our own species than do any invertebrates, however advanced. Their preconcieved dogma about what animals are contains a series of blatantly unscientific mandates: for instance, candidates for the distinction must boast such attributes as a certain number of legs, eyes of a specific proportion, and a very particular mastication mechanism. To them, anything which fails to explicitly conform to these and countless other arbitrary demands is mentally registered as having an unnatural appearance.

This phenomenon unambiguously explains the eccentric fascination one generally feels upon his or her first exposure to a reconstruction of Pantylus cordatus, a relatively small amphibian with a relatively ENORMOUS head.

Before granting further description to this bizarre little beastie, it’s neccessary to discuss the evolutionary relationships of the species, as per blog tradition. Pantylus is one of the best-known microsaurs, an extinct order of pint-sized lepospondyl amphibians which ranged from the late Carboniferous to the early Permian. For those intrigued by amphibian paleontology, I’d thoroughly reccomend Robert Carroll and Pamela Gaskill’s 214-page dispatch to the American Philosophical Society entitled “The Order Microsauria”, which can be read in full here. However, I shall quote a detailed excerpt concerning what exactly these critters were from another one of Carroll’s books: “The Rise Of Amphibians: 365 Million Years Of Evolution”.

“This group appears to be primarily terrestrial, but with secondarily aquatic adaptation in several families. Microsaurs are the most diverse of all the groups termed lepospondyls, in both numbers of species and adaptive and anatomical specializations…They are also the only clade that retains several skeletal attributes of early labyrinthodonts that suggest possible affinities…the earliest known microsaur is relatively long bodied, with approximately 34 presacral vertebrae. This, however, is not a general character of the group, as indicated by other skeletons from only slightly higher in the Carboniferous of Utah, and many later taxa that have much shorter vertebral columns and proportionately larger girdles and limbs. Other families of later microsaurs have reduced their limbs, but none have lost them entirely.

In contrast with most early labyrinthodonts, the jaw articulation in this and most other microsaurs does not extend beyond the occiput. The skull surface lacks the conspicuous sculpturing of most labyrinthodonts and there is no trace of lateral line canals. The eyes are about midway in the length of the skull and the surrounding bones are ridged along their circumference, suggesting a relatively thick layer of soft tissue above the bone…

The palate is not clearly visible in any of the skulls, but the surface shows an almost continuous covering of small denticle. One larger tooth extends from the palatine. The occiput is not well exposed, but the configuration of the surface for articulation with the atlas can be reconstructed on the basis of the latter bone… The lower jaw is not sculptured. The coronoid bones bear two rows of teeth…

Uniquely among Paleozoic amphibians, [the atlas] has a surface for articulation with the skull that is more than twice the width of the more posterior centra… The configuration of the occiptial condoyles and the anterior surface of the atlas in microsaurs would favor dorsoventral flexation of the head on the trunk and greatly limt lateral bending or rotation. In terms of its functional anatomy, this structure is highly divergent from that of labyrinthodonts and early amniotes, which have a multipartite atlas that would have allowed some degree of bending or rotation in all directions…

Ribs are visible throughout the trunk…the shafts are long and cylindrical…”

A sampler of microsaur diversity. From top to bottom: Tuditanus, Pantylus, Rhynchonkos, Cardiocephalus, and Pelodosotis.

Okay, then: now that I’ve displayed one of the longest quotes this blog has ever seen in order to adequately cover Pantylus’ family tree, let’s discuss the genus itself.

Pantylus skull

Pantylus is the namesake genus of the Pantylidae family, the members of which are primarily united by the following features:

-Deeply sculptured skull roofs.

-Triangular skull in aerial view.

-Short tail.

-24 presacral vertebrae and 1 sacral.

-Massive girdles and limbs.

-Four digits on each forelimb.

-A small number of blunt, conical, marginal teeth.

There’s relatively little else to say about Pantylus itself, other than giving mention to the fact that it’s easily the most well-known microsaur and among the most abundant, though its range appears to have been restricted to the Lower Permian red beds of Texas and would have reached approximately 25 centimeters in length: proving once and for all that you don’t have to supersize everything to achieve succuess in the Lone Star state…

May the fossil record continue to enchant us all!

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