Tag: artiodactyla

Island Weirdness #14 – Hoplitomeryx

During the mid-Miocene, about 15 million years ago, a region of central and southeast Italy around Gargano and Scontrone was cut off from the mainland by rising sea levels.

For the next 7-10 million years this island (or perhaps a cluster of islands) was left isolated, and an unusual ecosystem developed known as the “Mikrotia fauna”. With the island starting off lacking large predators, small herbivorous animals like rodents, pikas, and waterfowl became huge – and then small predators like gymnures and carnivorous birds also grew to keep up with the increasing size of their prey.

One of the strangest residents of the island(s) was Hoplitomeryx, an early type of ruminant that resembled a deer or pronghorn. Nicknamed the “prongdeer”, it had a total of five horns on its head and large protruding fangs similar to some modern deer.

Multiple species of Hoplitomeryx have been identified, representing four different size classes ranging from huge down to tiny insular dwarfs. The largest is estimated to have been similarly sized to modern moose, standing around 2m tall at the shoulder (6′6″), while the smallest would have been under 50cm (1′8″).

Each of these size classes was specialized for slightly different ecological niches, eating different types of vegetation to avoid directly competing with each other for the limited amount of food on the island.

Rayanistes

Remingtonocetids were an early branch of the whale evolutionary family tree, known from about 49-41 million years ago and splitting off somewhere between the famous “walking whale” Ambulocetus and the more oceanic protocetids. With otter-like bodies, tiny eyes, and long gharial-like snouts, they lived in near-shore shallow marine habitats and probably swam using a combination of their hind feet and tails.

They were initially found only in Pakistan and India, but then Rayanistes afer here was discovered all the way over in Egypt – suggesting that these early whales were much more widespread than previously thought, dispersing through the Tethys Sea at about the same time as their protocetid cousins.

Dating to the Middle Eocene (~45-41 mya), Rayanistes was probably about 2.5m long (8′2”). It had powerful hindlimb musculature that would have given it a very strong kicking swimming stroke, but it probably couldn’t actually support its own weight on land since its femur wasn’t very well anchored into its pelvis.

Eucladoceros

Eucladoceros dicranios, a deer from the Pliocene and Pleistocene of Europe (~3.5-1 mya). Close in size to a modern moose, standing about 1.8m tall at the shoulder (5′10″), the males of this species had a set of particularly large antlers – measuring up to 1.7 meters across (5′6″) and bristling with at least twelve prongs each – giving it the nickname of “bush-antlered deer”.

The more famous “Irish elk” (Megaloceros giganteus) would later develop even bigger antlers, but Eucladoceros was the earliest known deer to evolve this sort of extremely elaborate headgear.

Orcinus citoniensis

Despite commonly being called “killer whales” modern orcas are actually the largest living members of the oceanic dolphin family. Their ancestors are thought to have diverged from other dolphins between 10 and 5 million years ago – and surprisingly their closest relatives are the much smaller snubfin dolphins found in Australasia.

Living during the Pliocene (5-2 mya) in the Mediterranean, Orcinus citoniensis was an early member of the orca lineage, and was probably a transitional form between their early dolphin ancestors and the modern Orcinus orca.

It was half the size of modern orcas, at about 4m long (~13′). While it had a higher tooth count than its living relatives its teeth were also proportionally smaller, suggesting it wasn’t specialized for tackling large prey and probably fed mainly on fish and squid.

Waharoa

Waharoa ruwhenua, a whale from the Late Oligocene of New Zealand (~27-25 mya). Part of an early branch of the baleen whale lineage, it’s known from partial remains of an adult and a couple of juveniles and would have reached a full size of about 6m long (19′8″).

It had an unusually long flattened snout, with its nostrils further forward than modern whales, and only had baleen in the back half of its mouth – an interesting comparison to the intermixed teeth-and-baleen of some other early mysticetes. It’s not clear whether it had any vestigial teeth in the front of its jaws, although a single possible tooth has been found associated with its close relative Tokarahia.

The rather delicate nature of Waharoa’s jawbones suggests it wasn’t capable of rapid lunges at swarms of its small prey, instead probably using slow-cruising surface skim-feeding similar to modern right whales.

Inermorostrum

Inermorostrum xenops, a recently-named ancient cetacean!

Living about 30 million years ago in shallow coastal waters around the southeast USA, in what is now South Carolina, it was a member of one of the very earliest groups of toothed whales known as the xenorophids. Although only very distantly related to modern forms, xenorophids show evidence of being able to echolocate, suggesting the ability was probably ancestral to all toothed whales.

Estimated to have measured about 1m long (3′3″), Inermorostrum had a very short downturned snout and was completely toothless – specialized adaptations for suction feeding on small soft-bodied creatures on the seafloor.

Unusually for a toothed whale it also had proportionally large infraorbital foramina, openings in the bones of its snout for blood vessels and nerves to pass through. This suggests the presence of well-developed fleshy lips and possibly whiskers (as illustrated here), or maybe even an electroreceptive sense similar to some modern dolphins.

Ampelomeryx

Ampelomeryx ginsburgi, a palaeomerycid ungulate from the Early Miocene of France (~17 mya). About the size of a deer, around 1m tall at the shoulder (3′3″), it was a distant relative of modern giraffids.

Males sported three distinctive ossicone-like ‘horns’ – two over their eyes and a third forked one at the back of the skull – and protruding tusks like some modern deer, which probably served a similar purpose in fights against each other.

Ambulocetus

Ambulocetus natans, the Eocene “walking whale” – who might not actually have been able to walk at all!

A study published in 2016 suggests this early cetacean was actually fully aquatic and unable to support its own weight on land. So here’s an updated version compared to the Ambulocetus I did a couple of years ago.

Globicetus

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.

Unsolved Paleo Mysteries Month #14 – The Mystery Mega Mammal

During a 1923 expedition by the American Museum of Natural History to Inner Mongolia, China, a huge mammal skull was discovered dating to the Middle Eocene (~48-37 mya). About 83cm long (2′8″), with small low-set eyes, it was named Andrewsarchus mongoliensis in honor of expedition member Roy Chapman Andrews.

Almost a century later that one skull is still all we have. And despite this animal’s popularity among paleo-fans, we actually know very little about it.

It was originally classified as a mesonychian, leading to the many many depictions of it as a sort of “big bad wolf”. But more recent studies have placed it in the even-toed ungulates instead, with some suggestions that it might be most closely related to entelodonts, hippos, and whales.

Although it was certainly a big animal, it may not have been the giant “super predator” it’s often depicted as – its teeth aren’t particularly specialized and resemble those of entelodonts, suggesting it may have been more of an opportunistic omnivore than a dedicated carnivore.

Without more material we just don’t know for certain. So, frustratingly, the rest of Andrewsarchus’ body remains a mystery.

I’ve reconstructed it here based on one of its more obscure possible relatives: the anthracotheres, a group which may have been closely related to modern hippos. Scaling its body proportions to these animals produces rough measurements of about 1.45m tall at the shoulder (4′9″) and 3m long (9′10″), or about the same size as some of the big entelodonts or large modern bears.