Around 4m long (~13′), it had a long snout lined with small sharp teeth – unlike modern beaked whales which are mostly toothless – and much like its close relative Messapicetus it probably led a more dolphin-like lifestyle feeding on small fish near the surface.
It’s currently the youngest known example of a long-snouted stem beaked whale, a holdover from a time when these cetaceans were much more ecologically diverse than they are today.
Known from a partial skeleton about 12.7m long (~42′), it was much larger than earlier balaenids, but smaller than modern forms. It also had a narrower flipper shape compared to its modern relatives, a less arched jaw, and its neck vertebrae were only partially fused.
Modern right whales are slow-swimming ram feeders, but since Megabalaena was less specialized for this particular filter feeding style it’s unclear what its ecology was.
Albireonids were an early branch of the delphinoid whales, with their closest living relatives being modern oceanic dolphins, narwhals and belugas, and porpoises. Known from temperate latitudes of the North Pacific Ocean between the late Miocene and the late Pliocene, about 9-2.5 million years ago, their fossil remains are very rare in coastal deposits and they seem to have primarily been offshore open ocean animals.
Albireo whistleri is the best known member of this family, represented by a near-complete skeleton from what is now Isla de Cedros in Baja California, Mexico, dating to the late Miocene between about 8 and 6 million years ago. It was a rather small dolphin, around 2.5m long (~8’2″), with a stocky body, fairly broad flippers, and skull anatomy with some convergent similarities with the modern Dall’s porpoise.
Interestingly these dolphins also seem to have frequently had pathological neck vertebrae, with both Albireo whisteri and the younger species Albireo savagei from California, USA, showing unusually asymmetrical atlas bones – but on opposite sides to each other. This might be due to illness or injury earlier in life, or possibly be evidence of some sort of “handedness” with individuals preferring to perform some actions more with one side of their body than the other.
Although only known from a single fossil skull, this cetacean was probably around 3m long (~9’10”). It had a long snout lined with over 100 small pointed uniformly-shaped teeth, and the bony walls of its inner ears were well-preserved enough to show that it was able to hear narrow-band high frequency sounds – a specific form of echolocation that has convergently evolved multiple times in various modern and extinct toothed whale lineages.
Based on the presence of ancient river-mouth deposits in the area where Romaleodelphis was found, it may potentially have been capable of traversing between marine, brackish, and freshwater environments similar to the modern franciscana.
It was closely related to the waipatiids – a group traditionally classified as platanistoids (the South Asian river dolphin lineage), but more recently proposed as instead representing a separate earlier branch of the toothed whale evolutionary tree.
About 2m long (~6’6″), Aureia had distinctive tusk-like teeth that splayed outwards from its snout, interlocking when its mouth was closed. Along with a flexible neck and its fairly delicately-built skull and jaws, this suggests it was specialized for catching small prey in a “fish trap” of teeth, a unique feeding strategy for a toothed whale.
Along with different feeding specializations in other close relatives like Nihohae, Aureia shows us how multiple species of these ancient Aotearoan cetaceans were able to coexist in the same place and time by diversifying into different novel ecological niches.
Ninoziphius platyrostris was an early beaked whale that lived during the late Miocene (~6 million years ago) in warm coastal waters covering what is now southwestern Peru. Its ancestors appear to have branched off from all other beaked whales very early in the group’s history, indicating a “ghost lineage” going back to at least 17 million years ago.
About 4.4m long (~14’5″), it was less specialized for suction feeding and deep diving than modern beaked whales. Also unlike most modern species its jaws were lined with numerous interlocking teeth, with heavy wear suggesting it may have hunted close to the seafloor, where disturbed sand and grit would have regularly ended up in its mouth along with its prey and steadily ground down its teeth during its lifetime.
Males had a pair of stout tusks at the tip of their upward-curving lower jaw, with possibly a second smaller set of tusks behind them, which were probably used for fighting each other like in modern beaked whales.
Its shallow water habitat and more abrasive diet suggest Ninoziphius’ lifestyle was much more like modern dolphins than modern beaked whales, and other early beaked whales like Messapicetus similarly seem to have occupied dolphin-like ecological niches.
These dolphin-like forms disappeared around the same time that true dolphins began to diversify, possibly struggling to compete for the same food sources, while other beaked whales that had begun to specialize for deep sea diving survived and thrived. Interestingly this ecological shift seems to have happened twice, in two separate beaked whale lineages – although only one of them still survives today – with bizarre bony “internal antlers” even independently evolving in both groups.
While last week’s Tutcetus was the smallest known basilosaurid whale, another recently-announced member of that group was almost the complete opposite.
Living during the Eocene (~38 million years ago) in shallow marine waters covering what is now the coast of Peru, this ancient whale is known from several vertebrae, ribs, and parts of its pelvis. As a result its full size is uncertain, but based on the proportions of other basilosaurids it was probably somewhere around 17-20m long (~56′-66′) – similar in length to the larger specimens of Basilosaurus.
However, it had much thicker denser bones, even more so than those of its close relative Antaecetus, suggesting that its full body mass was much higher than the rather slender Basilosaurus – and possibly heavier than even modern blue whales despite being shorter in overall length.
Perucetus’ thickened vertebrae were also fairly inflexible in most directions, indicating it was a sirenian-like slow swimmer with limited maneuverability – but it did have a surprisingly good ability to bend its body downwards. Without skull material it’s unclear what its diet was like, but it may have been a suction-feeder hoovering up seafloor prey like modern grey whales or walruses.
I’ve reconstructed it here with a speculative bristly fleshy downturned snout inspired by the weird skull of Makaracetus, an earlier whale that may have also been a walrus-like bottom-feeder.
Tutcetus rayanensis was a whale that lived in warm shallow tropical seas covering what is now Egypt during the Eocene, about 41 million years ago.
It was an early member of the “basilosaurids“, a grouping made up of multiple early cetacean lineages (an “evolutionary grade“) representing some of the first fully aquatic forms. Like other members of this group it probably would have had a rather long and slender body shape – but unlike most of its relatives Tutcetus was comparatively tiny, estimated to only have been around 2.5m long (~8’2″).
The fusion of the skull bones in the one known fossil specimen indicate it was almost fully grown at the time of its death, and the pattern of tooth replacement suggests this small basilosaurid species matured very rapidly – a sort of “live fast, die young” life strategy.
Tutcetus’ small size and early demise also inspired its genus name, with “Tut” referencing the teenage Egyptian Pharaoh Tutankhamun.
Around 2m long (6’6″), it had unusually long tusk-like teeth at the front of its jaws, splaying out almost horizontally forwards and to the sides.
These teeth lay too flat to effectively interlock as a “fish trap”, and their fairly delicate structure and lack of wear marks suggests they also weren’t used for piercing large prey, sifting through gritty sediment, defending against predators, or for fighting each other. But Nihohae did have a highly flexible neck and the ability to quickly snap its jaws from side to side – although with a relatively weak bite force, suggesting it was primarily tackling small soft-bodied prey that could be easily swallowed whole.
Overall its feeding ecology seems to have been similar to modern sawfish, stunning prey such as squid with rapid slashing swipes of its jaws.
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.
