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!


The biggest known rodent of all time, Josephoartigasia monesi from the Pliocene and early Pleistocene of Uruguay, South America (~4-2 mya). Similar in size to a modern bison, it stood about 1.5m tall at the shoulder (4′11″) and weighed around 900kg (~2000lbs).

Despite looking like an extra-large capybara, it was only distantly related to the modern giant rodents. Its closest living relative is actually the much smaller pacarana.

Its 30cm long (12″) incisors could produce a large amount of bite force, and it may have used them in a similar manner to elephant tusks – rooting in the ground for food, stripping trees and branches, or defending itself from predators.


One of the earliest known dinosaurs, Herrerasaurus lived during the Late Triassic (~231 mya) in what is now Argentina, South America. It was a fairly lightly-built bipedal carnivore, with the largest specimens reaching sizes of just over 5m long (16′4″).

The exact classification of herrerasaurids is still somewhat unclear, with different analyses putting them in different positions on the early dinosaurian family tree. They’re generally considered to at least be closely related to basal theropods – but a recent analysis that reshuffles dinosaur relationships suggests their resemblance to the theropods might be a result of convergent evolution, with them being the sister group to sauropods instead.


Sirens are part of the salamander branch of the lissamphibians, and are some of the most unusual members of the group. They have an eel-like body shape, with small forelimbs and no hindlimbs at all, and have functional external gills as adults. Their main diet is carnivorous, with palatal teeth and a keratinous beak at the front of their jaws adapted for eating hard-shelled prey – but they’ve also been observed feeding on plant material, a rarity among amphibians.

Habrosaurus here was one of the earliest known sirens, living during the Late Cretaceous and Early Paleocene of North America (~84-58 mya). Reaching lengths of around 1.6m (5′3″), it was one of the largest known lissamphibians of all time, comparable in size to some modern giant salamanders.

It lacked the beak seen in its modern relatives, instead having specialized chisel-like teeth at the edges of its jaws that convergently served the same purpose of delivering a crushing bite.


Teleocrater rhadinus from the Middle Triassic (~245 mya) of Tanzania. Measuring about 2.5m long (8′2″), it was one of the earliest known members of the avemetatarsalians – the dinosaur-and-pterosaur (or “bird-line”) branch of the archosaurs. Its fossils have been known for over 80 years, but it was only very recently given an official name and classification following the discovery of additional specimens in 2015.

It turned out to be rather different from what paleontologists had expected an early bird-line archosaur to look like. Instead of being a bipedal basal-dinosaur-like animal, Teleocrater was actually a quadruped with more crocodilian-like limbs and oddly elongated neck vertebrae.

I’ve done two variations of the image today – both with and without a little speculative proto-fuzz.

An illustration of an extinct reptile related to the ancestors of dinosaurs and pterosaurs. It's a quadrupedal animal with a lizard-like head, a long neck, crocodile-like limbs, and a long tail.
Teleocrater rhadinus (no fuzz version)


Globicetus hiberus, a 5m long (16′4″) beaked whale from the Atlantic coast of Portugal and Spain. Its fossils can’t be easily dated since they were fished up from the seafloor, but it was probably around Early-to-Mid Miocene in age (~20-14 mya).

Its skull sported an odd bony sphere at the base of its snout, just in front of the melon, which appears to have been larger and more prominent in males than in females. Many modern beaked whales also have sexually dimorphic crests, ridges, and domes in their skulls, and these structures may function as sort of “internal antlers” – a display structure the whales can “see” via echolocation that signals their size, strength, and health to each other.


Utahraptor ostrommaysorum lived during the Early Cretaceous (~130-124 mya) in Utah, USA, and was the largest known dromaeosaurid. Reaching lengths of around 6m long (20′), it’s often compared in size to the fictional raptors of Jurassic Park.

Recent discoveries show it had some weird proportions compared to its relatives – a thick stocky body, chunky legs, smaller arms, a shorter and more flexible tail, and a large deep skull with an oddly curved lower jaw.

But we still don’t know very much about it… yet.

There’s a huge slab of rock full of Utahraptor fossils just waiting to be extracted and studied. There are at least six raptors in there ranging from babies to adults, hinting at the presence of a family group or even pack hunting behavior, and potentially other animals and new discoveries too – but the main roadblock for this project is lack of funding.

The paleontologists involved have turned to crowdfunding to attempt to raise enough money for essential equipment and the services of a professional fossil preparator, but they’re still only at about 10% of their goal.

So this first week of April is #UtahraptorWeek in the paleontology community, raising awareness of this fascinating giant raptor and how close we are to finding out so much more about it. Spread the word, and if you’re able to please consider helping out the Utahraptor Project on GoFundMe.

Unsolved Paleo Mysteries Month #23 – Puzzling Proto-Bats

Let’s finish off this month the same way we started: with flying vertebrates without any transitional forms!

Much like the pterosaurs, bats appear suddenly in the fossil record already fully flight-adapted. Despite being the second-largest group of mammals, bats’ small fragile bones and terrestrial habitats make fossils of them incredibly rare, and transitional forms are still entirely unknown. (Even the ancestral form illustrated above is a generic hypothetical mammal!)

The most “primitive” known bats come from the Early Eocene* (~55-52 mya) and various early representatives have been found as far apart as North America, Europe, India, and Australia – indicating they were already a widespread and diverse group by that time, and making it difficult to pin down just where and when they actually might have originated.

*I’ve seen mentions of a potential bat-like tooth from the Late Cretaceous of South America, but can’t find any actual references for it. So it’s possible bats may even have evolved before the K-Pg extinction.

Although bats were once thought to be related to archontans (treeshrews, colugos, and primates) based on morphological similarities, more recent genetic studies have shown them to instead be grouped with the laurasiatheres (eulipotyphylans, carnivorans, pangolins, ungulates, and whales). Based on this phylogenetic position the earliest ancestors of bats may have been small tree-climbing shrew-like animals who evolved flight while leaping in pursuit of insects. They might even be closely related to an obscure group called nyctitheriids – but without a lucky find of an exceptional fossil, we just don’t know.

Unsolved Paleo Mysteries Month #22 – Gargantuan Godzillus

During the summer of 2011 amateur paleontologist Ron Fine discovered an unusual fossil in northern Kentucky, USA. Beginning with an oddly-textured nodule, he gradually excavated a structure about 1m wide and 2m long (3′3″ by 6′6″) – far larger than any other fossil found in the area, and unlike anything seen before.

Dating to the Late Ordovician (~450 mya), and nicknamed “Godzillus” due to its massive size, the strange fossil has a roughly elliptical shape with what appear to be multiple branching lobes, and a surface texture made up of many rows of tiny bumpy “scales”. In some places small trilobites are found directly attached to it, most likely either feeding on it or sheltering.

The full “Godzillus” fossil and a close-up of its complex surface texture [Image source]

Although a paper has been published on Godzillus, it’s been given no official scientific name or classification. At best it’s been called an “organically textured surface”, with two different main possibilities suggested for its identity – either an algal mat that was deformed by water currents and smothered by a turbidity flow, or some sort of unknown upright soft-bodied organism that was toppled over and similarly buried.

Both hypotheses have their own strengths and weaknesses, and each explain some features of the structure but not others. So, for now, Godzillus remains a bizarre and unique fossil.

Unsolved Paleo Mysteries Month #21 – Ancient Aquatic Aliens

Found only in the Carboniferous-aged Bear Gulch Limestone (~318 mya) in Montana, USA, Typhloesus wellsi is such a confusing animal that it’s been nicknamed “the alien goldfish”.

It was one of the first body fossils found containing conodont elements, leading to it initially being identified in the 1970s as the then-unknown conodont animal – until actual conodont animals were discovered a few years later, looking nothing like it. The elements were reassessed as actually being Typhloesus’ gut contents, indicating it was actually a conodont-eating predator or scavenger.

Reaching sizes of almost 10cm long (4″), it was vaguely fish-shaped with a pair of ventral fin folds and a stiffened vertical tail paddle. No obvious sensory structures are preserved, but there are impressions of a large gut cavity in the front half of its body, along with a pair of strange unidentified organs known as “ferrodiscus” that contained a high concentration of iron deposits.

And despite being known from over 50 specimens, we still don’t know where to classify it. At all. It lacks evidence of features like gill openings or a notochord that could associate it with chordates. Its gut appears to be a blind sack with no anus, a condition usually seen only in cnidarians and flatworms, and finned active swimmers are known in other invertebrate groups like molluscs and arrow worms, but Typhloesus doesn’t resemble anything like those either.

With the similarly mysterious Tullimonstrum recently getting a lot of attention and a possible identification as a lamprey-relative, perhaps somebody will eventually have another look at this strange little creature, too.

[EDIT: A 2022 study found evidence of a molluscan affinity for Typhloesus!]