Acrophyseter

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Acrophyseter
Temporal range: Miocene (Serravallian to Messinian), 13.65–5.33  Ma
Acrophyseter deinodon skull.jpg
Holotype skull of A. deinodon
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Superfamily: Physeteroidea
Family: incertae sedis
Genus: Acrophyseter
Lambert, Bianucci & Muizon, 2008
Type species
Acrophyseter deinodon
Lambert, Bianucci & Muizon, 2008
Other species
  • Acrophyseter robustusLambert, Bianucci & Muizon, 2017

Acrophyseter is a genus of extinct sperm whale that lived in the Late Miocene off the coast of what is now Peru. The genus comprises two species: A. deinodon and A. robustus. It is part of a group of macroraptorial sperm whales that all share several features for hunting large prey, such as deeply rooted and thick teeth. Acrophyseter measured 4–4.5 metres (13–15 ft) in length, making it the smallest macroraptorial sperm whale currently known. Because of its short pointed snout and strongly curved front teeth, it probably fed on the large marine vertebrates of its time, such as seals and other whales.

Contents

History of discovery

Holotype skull of A. robustus Acrophyseter robustus holotype skull.png
Holotype skull of A. robustus

All known fossils of Acrophyseter, including those of the two named species, were discovered in the Pisco Formation, located in southern Peru. [1] The type species, A. deinodon, was described in 2008 by Olivier Lambert, Giovanni Bianucci and Christian De Muizon from a skull, catalogued MNHN SAS 1626, discovered in the Sud-Sacaco locality. [2] This site is dated between the Tortonian and Messinian stages of the Miocene, around 8.5–6.7 million years ago. The specimen represents a mature individual and consists of a skull and jaw with most of the teeth intact. [1]

In 2017, another species, A. robustus, was described by the same authors from a skull, catalogued as MUSM 1399, discovered in the Cerro la Bruja locality. This locality is older than Sud-Sacaco, dating between the Serravallian and Tortonian stages of the Miocene, at the least older than 9.2 million years. Later, a second A. deinodon specimen consisting of a right parietal bone was recovered from the Aguada de Lomas locality and recorded as MNHM F-PPI 272. The rocks at Aguada de Lomas are younger than both previously mentioned localities, and the specimen was dated to the Messinian stage of the Miocene, 6.9–6.7 mya. There have been doubts about its referral to A. deinodon, with some suggesting that it actually represents A. robustus instead. [1]

A third Acrophyseter skull, catalogued MUSM 2182, was discovered in the Cerro los Quesos locality, dating from the same period as Aguada de Lomas. Its specific attribution has not been formally established, [3] although it shares some similarities with the holotype skull of A. robustus. [1]

The genus name Acrophyseter is derived from the Greek akros—meaning acute, which describes the short, pointed, upturned snout—and physeter—which is the genus name for the modern sperm whale Physeter macrocephalus. The species name deinodon is from the Greek deinos—meaning terrible—and odon—tooth. [2] The species name robustus comes from Latin and references the thick bone constituting the edges of the supracranial basin and the base of the rostrum. [1]

Description

Upper and lower teeth Acrophyseter deinodon.jpg
Upper and lower teeth

Body length estimates for Acrophyseter range between 4–4.5 metres (13–15 ft). [3] A. deinodon was estimated to be 4–4.3 metres (13–14 ft) using the distance between the cheekbones in comparison to the dimensions of the related Zygophyseter. This makes it the smallest of the macroraptorial sperm whales. [1]

Unlike modern sperm whales, A. deinodon had teeth in both its upper and lower jaws. The teeth were robust and deeply set into the roots, particularly the front teeth, the tooth roots were comparatively thick when compared to the thin tooth crown. The front teeth were more conical than those further back in the mouth. The lower back teeth were tightly packed, and the space between the teeth increased from front to back, suggesting they were used in a shearing motion. This suggests a different feeding strategy from modern sperm whales, which all use suction-feeding due to a lack of teeth in the upper jaw. The front teeth were more worn on the sides, whereas the lower teeth were more worn along the middle. [2]

A. deinodon had 12 teeth in the upper jaw and 13 teeth in the lower jaw and posessed tooth enamel like other macroraptorial sperm whales. The premaxillae bore three teeth, and the maxillae had nine teeth. Unlike in other sperm whales, the top of the premaxillae near the vomer lacked a deep groove. [2] The last lower teeth may have contacted the roof of the mouth, [2] and cementum was continually added to the teeth as they were growing, as in killer whales (Orcinus orca). The tooth count of A. robustus is unknown, though it is thought to be similar to or the same as that of A. deinodon. [1] Discovered along the tooth sockets were buccal exostoses: bony growths which may have developed during biting to strengthen the teeth, acting as buttresses. The back teeth had larger buccal exostoses as they experienced more pressure during biting. [3]

Restoration of A. deinodon Acrophyseter deinodon restoration.jpg
Restoration of A. deinodon

Like other sperm whales, Acrophyseter had a deep basin on the top of its skull, the supracranial basin. This is overhung by the nuchal crest on the back of the skull. The supracranial basin, in turn, overhangs the orbit around the eye but does not extend onto the snout, unlike in other macroraptorial sperm whales. The temporal fossae on the sides of the skull were as high as they were long, unlike in Zygophyseter and Brygmophyseter. This displaces the brow ridge, which slopes down at an angle of around 55 degrees. Acrophyseter's cheekbones were thin plates which limited the ear canals. The snout was short and, unlike in other sperm whales, had a distinct upward curve. The masseter muscles, used in chewing, were located between the condyloid process, which connects the jaw with the skull, and the teeth. [2] Unlike later species of sperm whales, Acrophyseter had two nostrils. The left nostril was five times bigger than the right nostril, measuring 30 and 7.2 millimetres (1.18 and 0.28 in) across, respectively. [1]

Taxonomy

Acrophyseter belongs to a group of macroraptorial sperm whales together with Brygmophyseter , Livyatan and Zygophyseter. They all have large, deeply rooted teeth coated in enamel in both the upper and lower jaws and were adapted for hunting large prey items. [4] Macroraptorial sperm whales are thought to have either evolved these adaptations from a basilosaurid-like ancestor or independently once or twice within the group. [1] The extinct subfamily Hoplocetinae has been proposed to house this group, alongside the genera Scaldicetus , Diaphorocetus , Idiorophus and Hoplocetus . However, this grouping is paraphyletic, meaning it does not consist of a common ancestor and all of its descendants. [5] Relationships between Acrophyseter and other sperm whales are shown below, with the macroraptorial sperm whales in bold and the clades Kogiidae and Physeteridae collapsed. [1] [6]

Physeteroidea

Paleobiology

Features like the short, pointed snout, and robust, curved front teeth suggest that Acrophyseter targeted large prey. Their back teeth were potentially utilised in a shearing motion. It is thought that Acrophyseter would have preyed upon the numerous marine vertebrates that lived alongside it. [2]

Paleoecology

The localities of the Pisco Formation where remains of the animal have been found have yielded the remains of numerous marine vertebrates: the whales Piscolithax and Piscobalaena , the dolphins Brachydelphis , Atocetus iquensis, and Belonodelphis , the seal Acrophoca , the penguins Spheniscus urbinai and Spheniscus muizoni , the marine sloth Thalassocnus natans , the crocodile Piscogavialis, and the megalodon and broad-toothed mako sharks (Cosmopolitodus hastalis). [1] [2]

Related Research Articles

<span class="mw-page-title-main">Physeteroidea</span> Superfamily of toothed whales

Physeteroidea is a superfamily that includes three extant species of whales: the sperm whale, in the genus Physeter, and the pygmy sperm whale and dwarf sperm whale, in the genus Kogia. In the past, these genera have sometimes been united in a single family, the Physeteridae, with the two Kogia species in the subfamily Kogiinae; however, recent practice is to allocate the genus Kogia to its own family, the Kogiidae, leaving the Physeteridae as a monotypic family, although additional fossil representatives of both families are known.

<i>Thalassocnus</i> Extinct, aquatic ground sloth from South America

Thalassocnus is an extinct genus of semiaquatic ground sloths from the Miocene and Pliocene of the Pacific South American coast. It is monotypic within the subfamily Thalassocninae. The five species—T. antiquus, T. natans, T. littoralis, T. carolomartini, and T. yuacensis—represent a chronospecies, a population gradually adapting to marine life in one direct lineage. They are the only known aquatic sloths, but they may have also been adapted to a terrestrial lifestyle. They have been found in the Pisco Formation of Peru, the Tafna Formation of Argentina, and the Bahía Inglesa, Coquimbo, and Horcón formations of Chile. Thalassocninae has been placed in both the families Megatheriidae and Nothrotheriidae.

<i>Zygophyseter</i> Extinct genus of sperm whales

Zygophyseter varolai is an extinct sperm whale that lived during the Tortonian age of the Late Miocene 11.2 to 7.6 million years ago. It is known from a single specimen from the Pietra Leccese Formation in Italy. It was a member of a stem group of fossil macroraptorial sperm whales also including Brygmophyseter, Acrophyseter, and Livyatan. It probably grew to be around 6.5 to 7 meters in length and shared some characteristics with other raptorials, such as large teeth with tooth enamel that were functional in both the upper and lower jaws which the modern sperm whale lacks. It also had a beak, the ability to echolocate prey, and could have probably swum faster than the modern-day sperm whale which can reach 4 kilometers per hour (2.5 mph). These were probably used in the capture of large prey, such as large fish, seals, and whales. In fact, its common name, the killer sperm whale, refers to its feeding habits that would have had a resemblance to the modern-day killer whale.

<i>Brygmophyseter</i> Extinct genus of toothed whale (fossil)

Brygmophyseter, known as the biting sperm whale, is an extinct genus of toothed whale in the sperm whale family with one species, B. shigensis. When it was first described in 1994, the species was placed in the genus Scaldicetus based on tooth morphology, but this was later revised in 1995. In 2006, it was classified into the genus Naganocetus, which is considered to be a junior synonym. The only known specimen, a nearly complete skeleton, was dated to be around 16–15 million years old. Brygmophyseter is thought to have been 6.5–7 meters (21–23 ft) long, and it probably had 11 or 12 teeth in the upper and lower jaws. Brygmophyseter is part of a group of macroraptorial sperm whales which tended to be apex predators using their large teeth to catch struggling prey such as whales. It had a spermaceti organ which was probably used for biosonar like in the modern sperm whale. The whale has made an appearance on The History Channel's TV series Jurassic Fight Club.

<i>Livyatan</i> Extinct genus of sperm whale from the Miocene epoch

Livyatan is an extinct genus of macroraptorial sperm whale containing one known species: L. melvillei. The genus name was inspired by the biblical sea monster Leviathan, and the species name by Herman Melville, the author of the famous novel Moby-Dick about a white bull sperm whale. Herman Melville often referred to whales as "Leviathans" in his book. It is mainly known from the Pisco Formation of Peru during the Tortonian stage of the Miocene epoch, about 9.9–8.9 million years ago (mya); however, finds of isolated teeth from other locations such as Chile, Argentina, United States (California), South Africa and Australia imply that either it or a close relative survived into the Pliocene, around 5 mya, and may have had a global presence. It was a member of a group of macroraptorial sperm whales and was probably an apex predator, preying on whales, seals and so forth. Characteristically of raptorial sperm whales, Livyatan had functional, enamel-coated teeth on the upper and lower jaws, as well as several features suitable for hunting large prey.

<i>Orcinus citoniensis</i> Extinct species of killer whale

Orcinus citoniensis is an extinct species of orca identified in the Late Pliocene of Italy and the Early Pleistocene of England. It was smaller than the modern killer whale, 4 m (13 ft) versus 7 to 10 m, and had around 8 more teeth in its jaw. It may have resembled the modern killer whale in appearance, and could represent a transitional species between the modern killer whale and other dolphins. O. citoniensis could have hunted fish and squid in pods, and coexisted with other large predators of the time such as the orcinine Hemisyntrachelus and the extinct shark Otodus megalodon.

<i>Scaldicetus</i> Extinct genus of mammals

Scaldicetus is an extinct genus of highly predatory macroraptorial sperm whale. Although widely used for a number of extinct physeterids with primitive dental morphology consisting of enameled teeth, Scaldicetus as generally recognized appears to be a wastebasket taxon filled with more-or-less unrelated primitive sperm whales.

<span class="mw-page-title-main">Pisco Formation</span> Geologic formation in Peru

The Pisco Formation is a geologic formation located in Peru, on the southern coastal desert of Ica and Arequipa. The approximately 640 metres (2,100 ft) thick formation was deposited in the Pisco Basin, spanning an age from the Late Miocene up to the Early Pliocene, roughly from 9.6 to 4.5 Ma. The tuffaceous sandstones, diatomaceous siltstones, conglomerates and dolomites were deposited in a lagoonal to near-shore environment, in bays similar to other Pacific South American formations as the Bahía Inglesa and Coquimbo Formations of Chile.

<i>Albicetus</i> Extinct genus of mammals

Albicetus is a genus of stem-sperm whales that lived during the Miocene Epoch, around 15 million years ago, and was discovered in Santa Barbara, California in 1909. It was categorized for decades as belonging to a group of extinct walruses erroneously thought to be sperm whales. It was named Albicetus, meaning "white whale", is a reference to the leviathan in Herman Melville's classic 1851 novel Moby-Dick.

Liolithax is an extinct genus of dolphin from the Middle Miocene (Serravallian) Temblor Formation of California.

<i>Lophocetus</i> Extinct genus of dolphins

Lophocetus is an extinct genus of dolphin belonging to the clade Delphinida that is known from late Miocene (Tortonian) marine deposits in California and Maryland. Although usually placed in Kentriodontidae, recent studies have found it only distantly related to Kentriodon.

<i>Kogia pusilla</i> Small fossil whale from Italy

Kogia pusilla is an extinct species of sperm whale from the Middle Pliocene of Italy related to the modern-day dwarf sperm whale and pygmy sperm whale. It is known from a single skull discovered in 1877, and was considered a species of beaked whale until 1997. The skull shares many characteristics with other sperm whales, and is comparable in size to that of the dwarf sperm whale. Like the modern Kogia, it probably hunted squid in the twilight zone, and frequented continental slopes. The environment it inhabited was likely a calm, nearshore area with a combination sandy and hard-rock seafloor. K. pusilla likely died out due to the ice ages at the end of the Pliocene.

<i>Idiorophus</i> Extinct genus of mammals

Idiorophus is a genus of extinct toothed whales in the family Physeteridae. Fossils have been found in the Colhuehuapian Gaiman Formation of Argentina and the Libano Sandstone in Italy.

Eudelphis is an extinct genus of sperm whale belonging to Physeteroidea that lived in the ancient North Sea basin about 16-11 million years ago, during the middle Miocene (Langhian).

Inticetus is an extinct genus of Early Miocene odontocete from the Chilcatay Formation, Pisco Basin, Peru.

<span class="mw-page-title-main">Macroraptorial sperm whale</span> Predatory grouping of extinct whales

Macroraptorial sperm whales were highly predatory whales of the sperm whale superfamily (Physeteroidea) of the Miocene epoch that hunted large marine mammals, including other whales, using their large teeth. They consist of five genera: Acrophyseter, Albicetus, Brygmophyseter, Livyatan and Zygophyseter. All species are known by at least a skull, and are informally grouped without a family designation. They were all likely the apex predator of their habitats, comparable to the modern day killer whale, and achieved great lengths, with one species—Livyatan—measuring about 13.5–17.5 m (44–57 ft).

Hoplocetus is an extinct genus of raptorial cetacean of the sperm whale superfamily, Physeteroidea. Its remains have been found in the Miocene of Belgium, France, Germany and Malta, the Pliocene of Belgium and France, and the Pleistocene of the United Kingdom and South Carolina.

<i>Spheniscus muizoni</i> Extinct species of bird

Spheniscus muizoni is an extinct species of banded penguins that lived during the early Late Miocene in what is now Peru, South America. The species, the earliest member of the extant genus, was described in 2007 by Ursula B. Göhlich based on fossils found in the fossiliferous Pisco Formation of the Pisco Basin, southwestern Peru.

<i>Ankylorhiza</i> Extinct genus of toothed whales from the Oligocene epoch

Ankylorhiza is an extinct genus of toothed whale that lived in what is now the United States during the Oligocene epoch, between 29 and 23.5 million years ago. The type and only known species is A. tiedemani, though two fossil skeletons may represent an additional, second species within the genus. Ankylorhiza was about 4.8 meters (16 ft) long, with a long, robust skull bearing conical teeth that were angled forwards at the tip of the snout.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 Lambert, O.; Bianucci, G.; de Muizon, C. (2017). "Macroraptorial Sperm Whales (Cetacea, Odontoceti, Physeteroidea) from the Miocene of Peru". Zoological Journal of the Linnean Society. 179: 404–474. doi:10.1111/zoj.12456. hdl: 11568/814760 . Archived from the original on 22 July 2018.
  2. 1 2 3 4 5 6 7 8 Lambert, Olivier; Bianucci, Giovanni; Demuizon, Christian (2008). "A New Stem-Sperm Whale (Cetacea, Odontoceti, Physeteroidea) from the Latest Miocene of Peru". Comptes Rendus Palevol. 7 (6): 361–369. Bibcode:2008CRPal...7..361L. doi:10.1016/j.crpv.2008.06.002. S2CID   85723286. Archived from the original on 22 July 2018.
  3. 1 2 3 Lambert, O.; Bianucci, G.; Beatty, B. L. (2014). "Bony Outgrowths on the Jaws of an Extinct Sperm Whale Support Macroraptorial Feeding in Several Stem Physeteroids". Naturwissenschaften. 101 (6): 517–521. Bibcode:2014NW....101..517L. doi:10.1007/s00114-014-1182-2. PMID   24821119. S2CID   14542690. Archived from the original on 22 July 2018.
  4. Bianucci, G.; Landini, W. (2006). "Killer Sperm Whale: a New Basal Physeteroid (Mammalia, Cetacea) from the Late Miocene of Italy". Zoological Journal of the Linnean Society. 148: 103–131. doi: 10.1111/j.1096-3642.2006.00228.x .
  5. Toscano, A.; Abad, M.; Ruiz, F.; Muñiz, F.; Álvarez, G.; García, E.; Caro, J. A. (2013). "Nuevos Restos de Scaldicetus (Cetacea, Odontoceti, Physeteridae) del Mioceno Superior, Sector Occidental de la Cuenca del Guadalquivir (Sur de España)" [New Remains of Scaldicetus (Cetacea, Odontoceti, Physeteridae) from the Upper Miocene, Western Sector of the Guadalquivir Basin]. Revista Mexicana de Ciencias Geológicas (in Spanish). 30 (2). ISSN   2007-2902. Archived from the original on 22 July 2018.
  6. Berta, A. (2017). The Rise of Marine Mammals: 50 Million Years of Evolution. Baltimore, Maryland: Johns Hopkins University Press. pp. 112–113. ISBN   978-1-4214-2326-5. Archived from the original on 22 July 2018.