#polycotylidae

[alphynix]

While the most iconic types of plesiosaur were long-necked with small heads and short blunt snouts, some of these marine reptiles actually developed the opposite sort of arrangement, with groups like the polycotylids and the pliosaurs independently evolving short necks, larger heads, and long snouts.

…Except some of them didn't keep it quite that simple.

Serpentisuchops pfisterae here lived during the late Cretaceous, about 70 million years ago, in the ancient Western Interior Seaway covering what is now Wyoming, USA. This 7m long (~23') plesiosaur was a member of the polycotylid lineage, but along with a long slender snout it also had an unusually long neck.

Some earlier polycotylids like Thililua had fairly long necks, too, but all of Serpentisuchops' closest relatives were short-necked species, so it seems to have actually re-evolved this condition rather than inheriting it from its ancestors. Since no other marine reptiles in its habitat had this particular body plan, it was probably occupying a very specific ecological niche – the presence of attachment points for powerful neck muscles suggest it was able to swing its head sideways to snap its jaws at prey at high speed, with its longer neck giving it more reach than other polycotylids.

———

NixIllustration.com | Tumblr | Twitter | Patreon

[ildarotyrannus]

In the spring of last year, I made several color reconstructions of marine reptiles for a thesis and presentation (it was about the reconstruction of marine reptiles) for a conference that was held in Ulyanovsk in September. The drawings were done in ballpoint pen (lineart) and Paint Tool Sai 2.0 (shadows and colors).

The first is reconstruction of Mixosaurus cornalianus, a widespread small Triassic ichthyosaur. I had already drawn a Mixosaurus in water earlier and even wanted to use it in the article, but later changed my mind, deciding that lateral reconstruction would better convey the appearance of soft tissues. This earlier drawing can bee seen here:

Both pieces are based on the fin impressions described in 2020 from a specimen found in the Middle Triassic rocks of the Bezano formation, Italy (www.researchgate.net/publicati…). This specimen has preserved the tissues of the dorsal and caudal fins. Both prints have thin collagen filaments, and at the base of the caudal fin, it was possible to detect the remains of smooth, scaleless skin. The fins have a triangular shape, and the dorsal one is associated with 15-23 trunk vertebrae. In other words, its position turned out to be more

forward then in reconstructions done before his paper.

The second is lateral reconstruction of the metriorhynchid Cricosaurus albersdoerferi, belonging to a widespread genus that inhabited the shallow seas of future Europe, Central America and Argentina. It was not a particularly large animal, reaching from 2 to 3.2 meters in length. Like the first reconstruction of a Cricosaurus, which I performed in the spring, this drawing is based on a specimen that preserved a large volume of soft tissue on the tail (upload.wikimedia.org/wikipedia…). Also shown here is the salt gland in the antorbital fenestra, the presence of which was previously indicated in Cricosaurus araucanensis and Dakosaurus andiniensis. The spring work with C. albersdoerferi can be seen below:

Plesiosaurs are mentioned too. This is reconstruction of the polycotylid Mauriciosaurus fernandezi from the Late Cretaceous of Mexico. A complete reptile skeleton preserved in fine-grained rocks was described by a team of paleontologists in 2017: www.researchgate.net/publicati… There are five types of soft tissue imprints around the bones. Among them are dark material, probably left from the walls of the peritoneum, dark gray traces of blubber and impressions of possible small scales. The impressions show that the animal's belly was covered with rectangular scales, which were mixed with inclusions of small fragments closer to the limbs. The scales of the living reptile were almost indistinguishable, so that the skin looked smooth. This beautifully preserved specimen showed that plesiosaurs had much more soft tissue than previously thought. The tail was especially fleshy. Fat deposits created a smooth, streamlined shape, ideal for an agile swimmer.

The last thesis drawing is this reconstruction of the famous Early Jurassic ichthyosaur Stenopterygius quadriscissus. Many of its skeletons of amazing preservation were found in the fine-grained limestones of Holzmaden, Germany. Some of them were discovered back in the 19th century, which made it possible to quickly correct previous ideas about ichthyosaurs. The Stenopterygius specimens retained soft tissue prints in the form of a bacterial film, which made it clear that they were fish-like creatures with a dorsal fin and a crescent tail. They re still attract the attention of researchers. In 2018, the skin structure of one partial specimen was studied: www.researchgate.net/publicati… A fossilized blubber was described, similar in microstructure to that of marine mammals and leatherback turtles. This led to the conclusion that ichthyosaurs were reptiles with a high metabolism, which required fat insulation. Blubber allowed ichthyosaurs to travel across the oceans, swimming even into the cold polar waters. In addition, this Stenopterygius had pigment cells - melanophores. They were absent on the ventral side, which means that the Stenopterygius had a dark back and a light belly. This countershading coloring is typical of today's marine vertebrates and serves as a camouflage.

I did also three works in fully traditional style, with pens and pencils, but I'll show them in the separate post. :)

[megsdoodletag]

Unktaheela Specta breaching from the Western Interior Seaway on a sunny afternoon

[justgoji]

Serpentisuchops pfisterae, a polycotylid plesiosaur from late Cretaceous Wyoming.

With Hatsune Miku for scale:

[ancientmarinereptiles]

Mauriciosaurus fernandezi

Art by: Nobu Tamura, CC BY-SA 4.0

Name: ‭Mauriciosaurus fernandezi

Name Meaning: Mauricio’s reptile

First Described: 2017

Described By: Frey et al.,

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauria, Polycotylidae

Mauriciosaurus was a polycotylid plesiosaur that lived during the Late Cretaceous of what is now known as Mexico. We have a pretty well preserved juvenile specimen that was found in an area with lack of oxygen. The lack of oxygen is actually what helped preserve the soft tissues found within this plesiosaur. Preservation of soft tissues helped paleontologists see evidence of fat or blubber on Mauriciosaurus. So, to all paleoartists out there, please draw your plesiosaurs thicker than ever! This juvenile specimen was estimated to have been 6 feet (1.9 meters) in length.

Sources:

https://en.wikipedia.org/wiki/Mauriciosaurus

[infinitemachine]

Plesiosaur of the Day: Polycotylus Family by tiffanyturrill Polycotylus Family: Polycotylidae Time: Late Cretaceous Location: North America, Russia, and Australia Size (length): 5m (16ft) Note: Not a dinosaur

[alphynix]

Mauriciosaurus fernandezi, a polycotylid plesiosaur from the Late Cretaceous of Mexico (~94-89 mya). About 1.9m long (6′3″) with a flipper-span of 1.5m (4′11″), it’s known from a near-complete skeleton with preserved soft tissue impressions. The fossil shows evidence of rows of very tiny scales, the skin outlines of the flippers, and also a thick layer of insulating blubbery fat.

Its body shape in life would have been similar to modern leatherback turtles, roughly teardrop-shaped and hydrodynamic -- much chubbier than most plesiosaur reconstructions had been previously depicting!

[alphynix]

Mauriciosaurus, a plesiosaur with extensive soft tissue preservation – revealing that these marine reptiles had a thick layer of insulating fat in life.

[ancientmarinereptiles]

Manemergus anguirostris

Photo by: Ghedoghedo, CC BY-SA 4.0

Name: ‭Manemergus anguirostris

Name Meaning: Early/dawn diver

First Described: 2005

Described By: Buchy et al.,

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauria, Polycotylidae

We have another polycotylid found from Africa, just like ‭Thililua. Anyways, Manemergus was also discovered in the High Atlas Mountains in Morocco. Paleontologists recovered its skull, left femur, some of its phalanges, and some vertebrae.

Sources:

https://en.wikipedia.org/wiki/Manemergus

[ancientmarinereptiles]

Trinacromerum bentonianum‭‬,‭ ‬T.‭ ‬kirki

Photo by: Captmondo [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0/)]

Name: Trinacromerum bentonianum‭‬,‭ ‬T.‭ ‬kirki

Name Meaning: ‬Three tipped femur

First Described: 1888

Described By: Cragin

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauria,‭ ‬Polycotylidae‬

Trinacromerum was a polycotylid plesiosaur that actively swam the seas of the Western Interior Seaway during the Late Cretaceous. We know it was a quick and agile swimmer due to the length of its long flippers. Speed would definitely be required to hunt for fish, but also to avoid predation from other marine reptiles and even sharks back in the day.

Sources:

http://www.prehistoric-wildlife.com/species/t/trinacromerum.html

https://en.wikipedia.org/wiki/Trinacromerum

[ancientmarinereptiles]

Georgiasaurus penzensis

Art by: Andrey Atuchin, https://www.deviantart.com/olorotitan/art/Georgiasaurus-150470248

Name: Georgiasaurus penzensis

Name Meaning: ‬Georgy’s lizard (In honor of Georgy Otschev)

First Described: 1977

Described By: Otschev

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauria,‭ Plesiosauroidea,‭ ‬Polycotylidae‬

Georgiasaurus was a polycotylid from the Late Cretaceous. It was discovered in Russia and paleontologists unearthed part of its skull, some back vertebrae, and two of its flippers. This plesiosaur was originally going to be called Georgia, but that name was already taken, unfortunately.

Sources:

http://fossilworks.org/bridge.pl?a=taxonInfo&taxon_no=234698

https://en.wikipedia.org/wiki/Georgiasaurus

[ancientmarinereptiles]

Polycotylus latipinnis, P. sopozkoi

Art by: S. Abramowicz, Dinosaur Institute, NHM

Name: Polycotylus latipinnis, P. sopozkoi

Name Meaning: ‬Very cupped vertebra

First Described: 1869

Described By: Cope

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauria,‭ Plesiosauroidea,‭ ‬Polycotylidae‬, Polycotylinae

Polycotylus was a basal plesiosaur from the Late Cretaceous. Anyways, one really interesting fossil specimen (LACM 129639) was discovered with a fetus inside of it. The discovery of this amazing specimen helped paleontologists determine that Polycotylus and other plesiosaurs were most likely viviparous and gave birth to their young directly underwater. This completely shatters the obsolete idea that these marine reptiles hauled themselves on land to lay eggs or gave birth on land. In addition, the single fetus in the mother most likely meant that plesiosaurs used the K-selection strategy for caring/parenting their offspring. The K-selection strategy involves parent(s) dedicating more time and effort in raising typically one offspring at a time until they reach full maturity.

LACM 129639 specimen of P. latipinnis with fetus. Photo by: Dawn Pedersen [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

Sources:

http://www.prehistoric-wildlife.com/species/p/polycotylus.html

https://en.wikipedia.org/wiki/Polycotylus

https://en.wikipedia.org/wiki/R/K_selection_theory

[ancientmarinereptiles]

Sulcusuchus erraini

Photo by: Gasparini & Spalletti

Name: Sulcusuchus erraini

Name Meaning: ‬Trough crocodile

First Described: 1990

Described By: Gasparini & Spalletti

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauroidea,‭ ‬Polycotylidae‬

Sulcusuchus was actually a polycotylid plesiosaur that lived during the Late Cretaceous. It was unearthed in Argentina’s La Colonia Formation. It was originally thought to have been an ancient crocodile, hence the suffix ‘suchus’ of its generic name. Sulcusuchus was thought to have been an ancient crocodile from 1990 until 2013, 23 years later it was realized that it was really a plesiosaur.

Sources:

http://www.prehistoric-wildlife.com/species/s/sulcusuchus.html

https://en.wikipedia.org/wiki/Sulcusuchus

[ancientmarinereptiles]

Plesiopleurodon wellesi‭

Art by: Dmitry Bogdanov, CC BY 3.0

Name: Plesiopleurodon wellesi‭

Name Meaning: ‬Near Liopleurodon

First Described: 1996

Described By: Carpenter

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauria, Plesiosauroidea,‭ ‬Polycotylidae

This Late Cretaceous polycotylid swam the seas of the Western Interior Seaway of North America. It was discovered in the Hailey Shales Formation. What was found of Plesiopleurodon consisted of a complete skull, cervical (neck) vertebrae, lower mandible (jaws), and part of its right shoulder.

Sources:

http://www.prehistoric-wildlife.com/species/p/plesiopleurodon.html

https://en.wikipedia.org/wiki/Plesiopleurodon

[ancientmarinereptiles]

Pahasapasaurus haasi

Art by: Darrel Nelson, http://www.sdpb.org/blogs/images-of-the-past/the-haas-pleisiosaur-fossil/

Name: Pahasapasaurus haasi

Name Meaning: ‬Black Hills lizard (Paha Sapa meaning Black Hills in the Lakota language)

First Described: 2007

Described By: Schumacher

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauria,‭ Plesiosauroidea,‭ Polycotylidae‬

Pahasapasaurus was a polycotylid plesiosaur that lived during the Late Cretaceous. In 1934, it was found in South Dakota by farmer Charles Haas, so the specific name of this plesiosaur honors him. Pahasapasaurus was particularly discovered in a sandstone called Greenhorn Sandstone; the radius, ulna, tibia, and fibula bones were uncovered. In addition, a partial skull was found and paleontologists were able to examine the roof of its mouth. An abstract of an unpublished study describes the potential presence of salt glands housed within the nasal cavity of Pahasapasaurus that may have been preserved via fossilization. Salt glands would have allowed for the animal to avoid lethal dehydration by removing excessive salt from its body. 

Sources:

Schumacher, B. A. 2007. A new polycotylid plesiosaur (Reptilia; Sauropterygia) from the Greenhorn Limestone (Upper Cretaceous; lower upper Cenomanian), Black Hills, South Dakota. in Marin, J.E., and Parris, D.C., eds., The Geology and Paleontology of the Late Cretaceous Marine Deposits of the Dakotas: Geological Society of America Special Paper 427, p. 133-146.

https://en.wikipedia.org/wiki/Pahasapasaurus

[ancientmarinereptiles]

Palmulasaurus quadratus

Photo by: Albright et al.,

Name: Palmulasaurus quadratus

Name Meaning: Palmula lizard

First Described: 2007

Described By: Albright et al.,

Classification: Chordata, Tetrapoda, Reptilia, ‬Sauropterygia,‭ ‬Plesiosauria,‭ Polycotylidae‬

Palmulasaurus was discovered in Utah’s Tropic Shale Formation along with Eopolycotylus being found there as well. This polycotylid plesiosaur dates back to the Late Cretaceous. Initially it was named Palmula, but the name already belonged to a genus of foraminifera, so this plesiosaur’s name was then changed to Palmulasaurus.

Sources:

http://www.prehistoric-wildlife.com/species/p/palmulasaurus.html

https://en.wikipedia.org/wiki/Palmulasaurus