Mammalian tusks usually grow in symmetrical pairs with only minor developmental asymmetry, but a few species have evolved much more uneven arrangements.
Odobenocetops peruvianus
Odobenocetops peruvianus was a small toothed whale that lived during the Miocene, about 7-3 million years ago, in shallow coastal waters around what is now Peru. Around 3m long (~10′), it was a highly unusual cetacean with binocular vision, a vestigial melon, muscular lips, and a pair of tusks – features convergent with walruses that suggest it had a similar lifestyle suction-feeding on seafloor molluscs and crustaceans.
In males the right tusk was much more elongated than the left, measuring around 50cm long (~1’8″) in this species and up to 1.35m (4’5″) in the closely related Odobenocetops leptodon. Since these teeth were quite fragile they probably weren’t used for any sort of combat, and they may have instead served more of a visual display function.
The woolly mammoth (Mammuthus primigenius) lived across Eurasia and North America during the last ice age, mostly from the Pleistocene about 400,000 years ago to the early Holocene about 10,000 years ago – altohugh a few relict populations survived until around 4,000 years ago in isolated areas of Alaska, Siberia, and eastern Russia.
Around 3m tall at the shoulder (~10ft), these hairy proboscideans had very long curving tusks that were used for digging out vegetation from under snow and ice, scraping bark from trees, and for fighting.
The tusks showed a lot of variation in their curvature, and were often rather asymmetrical, a condition also seen in the closely related Columbian mammoth. Like modern elephants mammoths may have also favored using one side over the other for certain tasks, which over their lifetimes could result in uneven wear exaggerating the natural asymmetry even more.
Mammuthus creticus was originally thought to also be a palaeoloxodontine, but more recent studies of its anatomy and ancient DNA have confirmed it was indeed another tiny mammoth. It was probably descended from either the Southern mammoth or Mammuthus rumanus, which would have arrived on Crete during the late Pliocene or early Pleistocene between about 3.5 and 1 million years ago.
Isolated on Crete, with no predators and living at a time when the island was much smaller, it quickly dwarfed and became the tiniest known mammoth to ever exist, standing just 1.1m tall at the shoulder (3’7″). Not much is known about its ecology, but its teeth suggest it was a browser feeding on leaves and shrubs, possibly filling a similar niche to the mid-sized deer that came later.
This mini-mammoth seems to have gone extinct by the mid-Pleistocene, about 1 million years ago, around the time when rising sea levels during an interglacial phase may have submerged so much of the smaller proto-Crete that its population could no longer be supported.
Later in the mid-to-late Pleistocene, after the sea level dropped again and tectonic uplift brought Crete close to its modern dimensions, the small mammoths were replaced by both newly-arriving deer and Palaeoloxodon elephants, which evolved into the much more moderately dwarfed forms of Palaeoloxodon creutzburgi and Palaeoloxodon chaniensis.
Palaeoloxodon tiliensis
To the north and east of Crete the Cyclades and Dodecanese islands had endemic dwarf elephants on at least eight islands, with the best known being the species that lived on Tilos.
Palaeoloxodon tiliensis stood about 1.8m tall (5’11”), on the larger side for a dwarf Mediterranean elephant but still one of the smallest palaeoloxodontines in the Aegean region. Several thousand specimens have been found, and radiocarbon dating shows it was a fairly recent evolutionary development, appearing just 45,000 years ago in the late Pleistocene.
This dwarf elephant was also the very latest surviving of its entire kind, living well into the Holocene until at least 4000 BCE. This is several thousand years after humans first arrived on Tilos, suggesting it was a rare case of an island elephant that managed to endure the effects of a human presence for quite some time.
In fact there’s some speculation that Palaeoloxodon tiliensis (or a similar unknown species) may have survived for even longer than that, since one Ancient Egyptian tomb from around 1480-1400 BCE contains a painting depicting traders with exotic animals, including what appears to be a small hairy elephant with slender limbs and thin upward-curving tusks. We may never know for certain if this was actually a late-surviving dwarf, a mutant modern elephant, or just artistic license with scaling, but the possibility is still intriguing.
Palaeoloxodon cypriotes
Over on isolated Cyprus further to the east, the only native large mammals were the miniature hippos and an equally miniature elephant.
Palaeoloxodon cypriotes was smaller than the Aegean palaeoloxodontines, about 1.4m tall (4’7″), and much like its cousin on Tilos seems to have evolved very recently towards the end of the Pleistocene, sometime around 20,000 years ago.
It wasn’t the first dwarf elephant on Cyprus — there was a larger, earlier species known as Palaeoloxodon xylophagou at least 200,000 years ago — but it’s not clear whether these two species represent a single evolutionary line or two entirely different colonizations of the island.
Similarly to the hippos it lived alongside, Palaeoloxodon cypriotes disappeared shortly after humans arrived on Cyprus, between 12,000 and 10,000 years ago. Collections of its bones have been found in a rock shelter with evidence of having been burnt, suggesting that it was being actively hunted and cooked.
And that’s all for the Island Weirdness series! Even over two months there are still plenty of species I didn’t have time to feature, so this definitely won’t be the last we see of strange endemic species.
Thank you for following along — with a shoutout to my Patreon supporters! — and regular weekly art posts will resume here next Monday.
Mammuthus lamarmorai lived on the island of Sardinia during the middle and late Pleistocene, between about 450,000 and 40,000 years ago. Standing around 1.4m tall at the shoulder (4’7″), it was a dwarf form roughly one-third the size of its ancestor, the huge Eurasian steppe mammoth.
Its remains are known only from the west and south of the island. Strangely it appears to be have been absent from the nearby island of Corsica, despite the two being joined as a single landmass a few times during lower sea level periods in the Pleistocene.
It’s not clear why this mini-mammoth disappeared. The date of the earliest human settlement of Sardinia is controversial (ranging from 250,000 to 20,000 years ago), so Mammuthus lamarmorai might never have actually encountered them. Instead it may have struggled to cope with climate changes during the last glacial period towards the end of the Pleistocene, which rapidly turned Sardinia colder and drier.
Palaeoloxodon falconeri
Over on Sicily and Malta (which were also occasionally a single island when sea levels were lower), there were several different species of miniature elephant during the mid-to-late Pleistocene, each with a different body size and occupying its own ecological niche. They were all descendants of the massive straight-tusked elephant (Palaeoloxodon antiquus) but each resulted from independent colonization waves swimming over to the island(s).
Palaeoloxodon falconeri lived during the mid-Pleistocene, about 550,000 years ago, and was both the smallest of the Mediterranean dwarfs and possibly the smallest elephant to ever exist. Just 0.8-1m tall (2’7″-3’3″), it had adult body proportions resembling the juveniles of its ancestors, limbs adapted for running and clambering over rough terrain, and a proportionally enormous brain relative to its body size.
Around 200,000 years ago a sea level drop allowed new colonization from the Italian mainland. If Palaeoloxodon falconeri was still around at that time it likely didn’t survive long with new competition from large herbivores like bison and deer, and being preyed on by newly-arriving large carnivores like wolves, lions, and hyenas.
Another small elephant soon evolved to take its place, although due to the presence of predators it was never able to get nearly so tiny.
Palaeoloxodon mnaidriensis
Palaeoloxodon mnaidriensis was in fact one of the largest dwarf elephants in the Mediterranean, standing about 1.8-2m tall (5’11”-6’6″), but despite its larger size its limbs still show signs of adaptation for more fast and agile movement. Its tusks also show a lot of variation in shape, with some much more curved and twisted than others.
This elephant had disappeared by about 13,000 years ago, probably due to the climate significantly warming towards the end of the last ice age. Much like Sardinia, the earliest arrival of humans on Sicily and Malta is controversial, and it’s unclear whether they ever encountered Palaeoloxodon mnaidriensis — the earliest definite date for Sicily is about 16,000 years ago, so a human-induced extinction can’t be ruled out entirely.
The subfossil remains of the Siculo-Maltese elephants may have also ended up inspiring legends of the cyclops, as their skulls would have resembled large human ones with the nasal cavity forming a single big “eye socket”.
In the cool-temperate climate of Pleistocene Japan one type of small elephant seems to have convergently become somewhat of a mammoth-mimic, with twisting tusks and possibly even a thick coat of hair.
Palaeoloxodon naumanni
Palaeoloxodon naumanni lived during the late Pleistocene, between about 500,000 and 16,000 years ago. At about 2-2.5m tall at the shoulder (6’6″-8’2″) it was still fairly large, similar in size to the smallest living elephant species — but it was a dwarf in comparison to its immediate ancestors, the absolutely enormous Asian straight-tusked elephant (Palaeoloxodon namadicus).
Actual woolly mammoths (Mammuthus primigenius) were also present in Japan, but the two similar-looking elephants inhabited different environments — Palaeoloxodon naumanni preferred the southern forests, while the true mammoths roamed the colder north.
Humans arrived in Japan around 40,000-30,000 years ago, so Palaeoloxodon naumanni actually coexisted with them for quite some time. Although it was hunted, it seems to have mainly been climate change towards the end of the last glacial maximum that led to its extinction.
Mammuthus exilis
Over on the other side of the Pacific Ocean, at least 60,000 years ago, some huge Columbian mammoths (Mammuthus columbi) swam the 6.5km (4 miles) distance to the ancient island of Santa Rosae — a landmass that today is mostly submerged, with its remaining peaks forming the modern California Channel Islands.
With a lack of large predators and then steadily rising sea levels reducing the available habitat on their new home, the mammoths shrank into a dwarfed species known as the Channel Islands pygmy mammoth (Mammuthus exilis). Standing around 1.75-2m at the shoulder (5’9″-6’6″), they were less than half the size of their ancestors and had only about 10% of the body mass.
The pygmy mammoths survived until about 13,000 years ago, around the same time that early Paleoindians arrived. While they may also have been hunted by humans, the warming post-glacial climate is currently thought to be the main factor in their extinction, changing the types of vegetation on their still-shrinking islands and reducing fresh water sources.
We left off last time with the dwarf stegodontids of Flores, but other Indonesian islands also had their own populations of unusually small elephant-relatives — so here’s a few more to start off this month!
Sinomastodon bumiajuensis
Sinomastodon bumiajuensis lived on the island of Java during the early Pleistocene, about 2-1.5 million years ago. It stood around 2m tall at the shoulder (6’6″), less than half the size of most other Sinomastodon species from mainland Asia. Although it looked convergently similar to modern elephants it was actually a member of the gomphotheres, much more closely related to the weird “shovel-tuskers” than to any living species.
Stegodon semedoensis
Stegodon semedoensis, also from the early Pleistocene of Java about 1.5 million years ago, is only known from a few isolated molar teeth — but the size of those teeth suggest it was one of the smallest known pygmy stegodontids. It was probably no more than 1.2m at the shoulder (3’11”), comparable in size to its close relative Stegodon sondaari over on Flores.
Elephas celebensis
Meanwhile on Sulawesi, Elephas celebensis (sometimes called Stegoloxodon celebensis) was an actual true elephant closely related to the modern Asian elephant. Living during the late Pliocene and early Pleistocene, between about 2.5 million and 800,000 years ago, it was only 1.5m tall (5′) and had a second set of tusks in its lower jaw, a “primitive” feature retained from the gomphothere-like ancestors of modern elephants.
Stegodon sompoensis
At the same time Sulawesi also had yet another small stegodontid, Stegodon sompoensis, also around 1.5m tall.
The cooling climate of the Pleistocene and dropping sea levels eventually connected the islands of western Indonesia to the Sundaland landmass of mainland Asia. Influxes of new predators and competitors — and early humans — probably drove these endemic small elephants to extinction.
Much like Japan, ancient Flores had a succession of dwarf stegodontids – close relatives of modern elephants that were capable of island-hopping through Indonesia by swimming.
Stegodon sondaari
Stegodon sondaari lived on Flores during the Early Pleistocene, about 900,000 years ago, and was the size of a small water buffalo at just 1.2m (3′11″) tall at the shoulder. It was probably descended from the larger Stegodon trigonocephalus, known from Java, and it had proportionally short legs which may have been an adaptation to clambering over rough terrain and steep inclines.
Around 850,000 years ago Stegodon sondaari disappeared from Flores, probably due to a large volcanic eruption, but a new wave of stegodontids quickly recolonized the island. The mid-sized Stegodon florensis probably originated from either Java to the west or Sulawesi to the north, and eventually evolved into a new dwarfed subspecies.
Stegodon florensis insularis
Stegodon florensis insularis wasn’t quite as small as its predecessor, standing around 1.8m tall (5′10″). It probably didn’t shrink quite so much due to the existing presence of various predators on Flores, since it was likely the main prey of large Komodo dragons, it was hunted by Homo floresiensis, and it may also have been occasionally targeted by giant storks.
It seems to have disappeared around the same time as several other unique endemic species, between 50,000 and 20,000 years ago, due to either climate change, another volcanic eruption, or the arrival of modern humans – or perhaps a combination of all of those factors.
And that’s all for this month… but Island Weirdness will be back later for part 2, with more giants, more dwarfs, and so many elephants.
Part of the “island rule” is that large animals often become smaller – and no group seems to exemplify this more than the elephants.
Although they’re the largest living land animals today, and in the past included some of the largest known land mammals ever, ancient elephants also frequently ended up on islands thanks to their ability to swim long distances. They produced many different dwarfed forms around much of the world, and a few of them will be featured intermittently throughout both months of this theme.
The earliest known examples were the stegodontids of Japan in the early Miocene. These animals weren’t quite true elephants, instead being close evolutionary cousins to them, and had two small additional tusks in their lower jaws similar to the related gomphotheres.
Stegolophodon pseudolatidens
Stegolophodon pseudolatidens first arrived in Japan about 18 million years ago, and within just 2 million years they’d developed into insular dwarfs that were probably around 2m tall at the shoulder (6′6″)– still reasonably large, but only about 60% the size of their mainland relatives.
Stegodon aurorae
Much later in the Early Pleistocene another small almost-elephant appeared in Japan. Living between about 2 million years ago and 700,000 years ago, Stegodon aurorae was about the same size as the then-extinct Stegolophodon but probably wasn’t descended from them. Instead it was probably the result of a separate arrival and dwarfing of a larger Stegodon species from mainland Asia.
