Tag: jamaica

Hyrachyus

What’s the most unexpected fossil you’d think could be found on the island of Jamaica?

How about an ancient rhino?

Hyrachyus here was an early member of the rhinocerotoids, a lineage of odd-toed ungulates that also includes the true rhinoceroses, the tapir-like and hippo-like amynodontids, the long-legged hyracodontids, and the giant indricotheriines.

This particular genus was very widespread for much of the Eocene, found across Europe, Asia, and North America, crossing back and forth between the continents via the North Atlantic land bridge.

The Jamaican Hyrachyus lived during the mid-Eocene, around 45 million years ago, and was very anatomically similar to the North American Hyrachyus affinis – with the known fossil material not being considered distinct enough to be assigned to a new species yet. It was also about 15-20% smaller than its mainland relative, standing only 25cm tall at the shoulder (10″), but it’s not yet clear if this was a case of insular dwarfism or not.

Its presence in ancient Jamaica suggests that there may have been some sort of land connection between the proto-island and Central America during the early Eocene, when a chunk of what would eventually become western Jamaica was located much closer to the coasts of Honduras and Nicaragua. It’s the only fossil ungulate known from the Caribbean, and one of only a few terrestrial mammals in the region with North American evolutionary roots (the others being the extinct rodents Caribeomys merzeraudi and Oryzomys antillarum, and modern solenodons).

Unfortunately these little rhinos didn’t get much time on their island home. Jamaica subsided fully underwater about 40 million years ago, drowning its unique Eocene ecosystem entirely, and wouldn’t re-emerge and be re-colonized until much later in the Cenozoic.

Island Weirdness #50 — Caracara tellustris

Jamaica is unusual among the Caribbean islands for having had relatively few predatory birds.

One of the few known fossil species is Caracara tellustris, a close relative of the modern crested caracaras that probably evolved in the mid-Pleistocene between about 1.2 and 0.4 million years ago.

About 60-65cm long (2′-2’2″), it was similar in body size to larger individuals of its living relatives but was heftier built and had slightly longer legs, and its wings were reduced enough that it was either a very weak flier or entirely flightless.

It lived only in the dry scrubland around the southern coast of the island, and probably mainly preyed on reptiles, small rodents, and crabs using its strong legs — a lifestyle very similar to the modern secretarybird. Like other caracaras it would have also opportunistically scavenged on carrion, which there would have been little competition for.

The known remains of Caracara tellustris date to as recently as 100 CE, showing that it existed well into the Holocene and survived through the initial arrival of humans on its island home (about 4000 BCE). This is likely due to its inhospitable hot, arid, and thorny habitat, where it would have been left relatively undisturbed, and it may even have persisted until the time of European colonization in the 1500s.

Unfortunately the scrubland was also very limited in size and the Jamaican caracara would have always been quite a rare species. If it was still around by then it would have faced a combination of introduced predatory mammals and habitat destruction by agriculture, which would have driven it into extinction so quickly its existence was never even noticed by naturalists at the time.

Island Weirdness #49 — Sloth-Monkeys & Fighting Ibises

Jamaica is the third largest island in the Caribbean, and much like Cuba it originated as part of a Late Cretaceous volcanic island arc. It began to subside during the Eocene and was completely submerged for a large portion of the Cenozoic, then was uplifted again in the early-to-mid Miocene, reaching close to its present-day size around 13 million years ago.

Few land mammals ever colonized the island prior to human influence, and most of the known remains are from rodents. But another group did make it onto Jamaica, and became something especially weird.

A stylized illustration of an extinct titi monkey. It has long soft fur and a very long tail.
Xenothrix mcgregori

Xenothrix mcgregori is a primate only known from fragmentary remains, but what is known of its skeleton shows a unique combination of features for a New World monkey. It had a reduced number of teeth in its jaws, with enlarged molars, and oddly-shaped heavily-built leg bones that resemble those of slow quadrupedal climbers like lorises.

It was probably about 70cm long in total (2’4″), including the tail, and is thought to have lived a lot like a tree sloth, spending most of its time moving slowly around in the trees and possibly even feeding while hanging upside down.

Its anatomy was so ununsual that its evolutionary relationships were a mystery until ancient DNA was recovered from subfossil bones and confirmed it was actually a titi monkey very closely related to the genus Cheracebus. Its ancestors probably arrived on Jamaica in the late Miocene, around 11 million years ago, and it had some close relatives on a couple of other Caribbean islands — the terrestrial Paralouatta on Cuba, and Antillothrix and Insulacebus on Hispaniola — although they likely all independently colonized the Caribbean via different rafting events from South America.

A stylized illustration of an extinct flightless ibis. It has stout legs, and has its wings raised as if threatening to hit something with its heavy club-like arm bones.
Xenicibis xympithecus

Another inhabitant of Jamaica was an equally strange bird.

Xenicibis xympithecus was one of only two lineages of ibis ever known to have become completely flightless (the other being Apteribis from Hawaii).

Around 60cm tall (2′), it had some of the most unique wings of any bird. The hollow bones were thickened, its forearm was proportionally short, and the hand was modified into a large heavy “club” — and blunt-force injuries on some of these birds’ remains suggest that they used their wings as weapons when fighting, clobbering each other with powerful blows.

Radiocarbon dating suggests the Xenothrix monkeys survived well into the Holocene, until around 1100 CE. Since various groups of humans had been present on Jamaica since about 4000 BCE the sloth-monkeys must have coexisted with them for several millennia, and their extinction may have been caused by more of a “slow fuse” of gradual habitat destruction than direct exploitation.

Dating on Xenicibis‘ extinction is less precise, with the youngest known remains being somewhere between 10,000 and 2200 years old. It may have still been around when the earliest humans arrived, but unlike the native monkeys it seems like it didn’t last long beyond that point.

Jamaican flightless ibis

The Jamaican ibis (Xenicibis xympithecus) was a bird unique to the Caribbean island of Jamaica. One of only two known types of completely flightless ibises, it was similar in size to a chicken – probably around 75cm long (2′5″) and weighing 2kg (4.4 lbs).

It had some incredibly unusual wing anatomy, with strengthened bones, a proportionally short forearm, and the “hand” section modified into a thick club-like shape. Some remains show evidence of blunt-force injuries, suggesting these birds fought each other by swinging around their heavy wings like baseball bats.

Its bones have found in several cave deposits which are difficult to accurately date, but are likely to be somewhere between 10,000 and 2,200 years old. It’s unclear whether Xenicibis was still around when humans first colonized the island, but if so it was probably driven to extinction soon after.