Thursday, July 4, 2013

Wrinkly Greasy Inostrancevia

Inostrancevia was a genus of gorgonopsid, living in what is now Siberia during the Permian period.  This area was a hot, dry desert during this time.  Close relatives of the ancestors of all mammals, gorgonopsids very likely had leathery, glandular skin, and also hair, though likely not in the role of thermoregulation.  Gorgonopsids were fox- to lion-sized carnivores with well-developed nasal turbinates, indicating an active hunting lifestyle, though not necessarily a well-developed sense of smell.  They did have a vomeronasal organ, though, and would have hunted by scent much like a monitor lizard.  Inostrancevia was the biggest known, with a skull about two feet in length.  Here, I've hypothesized a role for an early wet nose, coupled with ancestral hair follicles acting in a possible precursor role of guards/wicks for mucus and sebaceous glands.  In my hypothetical restoration, mucus-wicking hairs poking out of the ancestral philtrum (cleft upper lip of modern mammals, less developed here and hypothetically comprising two parallel grooves) would collect airborne scents, which are collected by a flick of the tongue and passed across the vomeronasal organ to be detected.  Glandular secretions of oily, waxy sebum (or a related substance) would have kept skin moist and pliable where flexibility was needed more than the toughness of cornified, callused skin.  Fur was unlikely at this time, becoming more useful to later relatives in nocturnal habits as therapsids in general became marginalized by the upstart archosaurs (dinosaurs and kin).

I'm inspired by modern naked-skinned tropical mammals like hippos, rhinos, and Xoloitzcuintle dogs

Software: OpenCanvas 5.5

7 comments:

Vinod Rams said...

beautiful! And very well researched and thought out.

Jason Scheier said...

your such an inspiration man

Metal snail said...

Great work Matt, I love those wrinkles!

Fabio Manucci said...

Awesome!

Ramon said...

This is fantastic!

nwlorax said...

They would have possibly slept under tree cover during most of the day and hunted early morning or at night, reducing their daytime thermal load and conserving water, while their active metabolism would have allowed for some sort of stalk, attack and takedown, even without a diaphragm, which I think was still lacking (yes?). If all four of the visual pigmentreceptor sets (absent in most true mammals but found in reptiles) were still present in these beasties, with a tapetum lucidum they could have stood up or braced up on a tree for some additional height and looked out for night movements of possible prey.

Is there any evidence for or against an external ear, even a simple one? If not, could they have put their heads to the ground and gotten low frequency sounds of herds moving around?

MCBarrett said...

I'd guess they were still tetrachromats, but the tapetum lucidum is less certain. It's a feature that pops up independently in several distinct lineages, and with different structures and mechanisms in each. I don't think there are many, if any, sclerotic rings preserved for synapsids of this grade, so it's difficult to estimate pupil size. The size of the eye socket isn't as diagnostic as one might expect, since soft tissues can vary considerably in bulk.
They did likely have an external ear structure. The early eardrum of stem-mammals was a membrane stretched across a concavity on the rear surface of the lower jaw. It's likely this would have been protected by folds of skin, possibly stiffened to remain open during jaw movement (which is rather more dynamic overall than the skull-based jaw abductor muscles of diapsids) with loops of cartilage. I've rendered a simple ear canal, kept clear of dust by hair follicles and sebaceous glands. External ear pinnae would be descended from this early cartilaginous tube and loop.
The presence of a diaphragm is difficult to be certain about, but a gradually-tapering ribcage more similar to pelycosaurs than to, say, dogs, would suggest it at least didn't have a fully-mammalian breathing mechanism. I suggested a monitor-style hunting method for this reason, since modern perenties employ buccal pumping (with highly modified cervical ribs and hyoid bones) to supplement their gait-limited breathing mechanisms while patrolling. There's a possibility that some large gorgonipsids were venomous, however, and it may have been a sequential ambush-hunter/scavenger like modern Komodo monitors. Perhaps it charged into a huddle of pareiasaurs sheltering from the heat, envenomated the slowest to rise, and spent another day or so tracking down its meal wherever it eventually succumbed.
I think feline/hyaenid style nighttime stalking is hard to support without firm evidence of strong night vision ad acute hearing.