Macroraptorial sperm whale

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Skull of Livyatan Livyatan melvillei skull.jpg
Skull of Livyatan

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 . [1] 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 (Orcinus orca), and achieved great lengths, with one species— Livyatan —measuring about 13.5–17.5 m (44–57 ft).

Contents

Discovery

Zygophyseter was discovered in the Pietra Leccese Formation in Italy from a skull, teeth, and vertebrae; [2] Brygmophyseter was discovered in the Bessho Formation in Japan from a nearly-complete skeleton; [3] and Acrophyseter and Livyatan both originate from the Pisco Formation in Peru and are known by only a skull. [4] Albicetus is discovered from Santa Barbara Lighthouse in 1909, which is believed to most likely be part of the Monterey Formation. It was first classified within the genus Ontocetus (now a genus of walrus), and then moved to a wastebasket taxon Scaldicetus until Boersma and his colleagues gave a new generic name. [5]

Description

Upper and lower tooth rows of Acrophyseter Acrophyseter deinodon.jpg
Upper and lower tooth rows of Acrophyseter
Macroraptorial body length range [5] [6]
GenusSIImperial
Acrophyseter ≈4–4.5 m≈13–15 ft
Albicetus≈5.9–6.3 m≈19–21 ft
Brygmophyseter≈6.5–7 m≈21–23 ft
Zygophyseter≈6.5–7 m≈21–23 ft
Livyatan≈13.5–17.5 m≈44–57 ft

Macroraptorial sperm whales had large, functional, conical teeth in both jaws, as opposed to the modern sperm whale whose teeth are small and nonfunctional in the upper jaw. The teeth were deeply rooted into the gumline and could interlock, probably to aid in holding struggling prey. The teeth of Livyatan, at a length of 31 cm (12 in), were one of the biggest teeth of any animal, excluding tusks. The macroraptorials also had well-developed muscles used in biting—the temporalis and masseter. They also developed buccal exostoses in the mouth, bony growths which act as buttresses during biting, further increasing the bite force. [2] [3] [4] [6]

Like modern sperm whales, the macroraptorials had a curved basin—the supracranial basin—on the top of the skull. This encompassed the entire breadth of the snout in Livyatan and Brygmophyseter; [3] [7] Zygophyseter and Acrophyseter, instead, had reduced basins indicating beaks. [2] [4] The elongated lumbar vertebrae of Zygophyseter indicate it had larger multifidus and longissimus back muscles and was, thus, faster than the modern sperm whale which, [2] comparable to other large open-ocean animals, travels horizontally at 4 km/h (2.5 mph). [8]

Paleobiology

Macroraptorial sperm whales occupied the same niche as killer whales (Orcinus orca). Orcas in Alaska.jpg
Macroraptorial sperm whales occupied the same niche as killer whales (Orcinus orca).

Using their large and deeply rooted teeth, wide-opening jaws, and great size, they likely fed on a variety of sea life, including fish, cephalopods, seals, and small whales and dolphins, occupying a niche similar to the modern day killer whale (Orcinus orca). [4] [7] [9] In fact, Zygophyseter is known colloquially as the "killer sperm whale" in reference to this. [9] Likewise, they may have employed a similar hunting strategy of pursuing prey to tire it out before eventually drowning it. However, given their size, they probably did not need to hunt in groups. Livyatan probably targeted medium-sized whales ranging in size from 7–10 m (23–33 ft). Macroraptorials probably competed with the extinct giant shark megalodon for the same food sources. [7] [10] [11] [12]

In sperm whales, the supracranial basin holds the spermaceti organ, a series of oil and wax reservoirs which aids in echolocation. Speculatively, the organ may also serve a secondary function, such as vocalizing, acoustic stunning of prey, head-butting between males, ramming into prey, or buoyancy control by increasing or decreasing the temperature of the wax to change the density and weight. [7]

Taxonomy

Brygmophyseter skeleton Brygmophyseter skeleton (cropped).jpg
Brygmophyseter skeleton

The macroraptorial sperm whales are a paraphyletic fossil group of hyper-predatory stem sperm whales. All share large, functional, enamel-coated teeth on both the upper and lower jaws, which were used in capturing large prey. In contrast, the modern sperm whale (Physeter macrocephalus) lacks enamel, teeth in the upper jaw, and the ability to use its teeth to catch prey. [13] However, Livyatan belongs to a different lineage than the other macroraptorials, and the development of large size and the spermaceti organ, an organ that is characteristic of sperm whales, are thought to have evolved independently from the other macroraptorials. The large teeth either evolved once in the group with a basilosaurid-like common ancestor, or independently in Livyatan. The large temporal fossa depressions on the skull of raptorials is probably descended from a common ancestor (plesiomorphy). The presence of enamel is thought to be an ancient and basal characteristic, as it is present on the teeth of fetal modern sperm whales. Macroraptorials appeared during an adaptive radiation event of baleen whales in the Miocene, an increase in whale populations and diversity, implying the macroraptorials evolved specifically to exploit baleen whales. [4] [7] A 30 cm (12 in) tooth found in Australia indicates macroraptorials still existed 5 mya in the Pliocene. [14]

Restoration of Zygophyseter Zygophyseter BW.jpg
Restoration of Zygophyseter

It has also been suggested that the macroraptorials be placed into the subfamily Hoplocetinae, a subfamily characterized by robust and enamel-coated teeth, alongside the genera Diaphorocetus , Idiorophus , and Hoplocetus , which are known from the Miocene to the Early Pleistocene. However, most of these whales are known from fragmentary remains or have been used as wastebasket taxa for indiscernible stem sperm whale remains. [9]

Physeteroidea
Macroraptorials are in bold [4] [5] [7] [13]

See also

Related Research Articles

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

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<span class="mw-page-title-main">Kogiidae</span> Family of mammals

Kogiidae is a family comprising at least two extant species of Cetacea, the pygmy and dwarf sperm whales. As their common names suggest, they somewhat resemble sperm whales, with squared heads and small lower jaws, but are much smaller, with much shorter skulls and more notable dorsal fins than sperm whales. Kogiids are also characterized by a "false gill slit" behind their eyes.

<span class="mw-page-title-main">Megalodon</span> Extinct giant shark species from 23 to 3.6 million years ago

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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, the 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>Acrophyseter</i> Extinct genus of sperm whales

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.

<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>Diaphorocetus</i> Extinct genus of mammals

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<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

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<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.

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

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

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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).

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>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. ↑ Peri, Emanuele; Falkingham, Peter L.; Collareta, Alberto & Bianucci, Giovanni (2021). "Biting in the Miocene seas: estimation of the bite force of the macroraptorial sperm whale Zygophyseter varolai using finite element analysis". Historical Biology. 34 (10): 1916–1927. doi: 10.1080/08912963.2021.1986814 . hdl: 11568/1117056 .
  2. 1 2 3 4 Bianucci, Giovanni; Landini, Walter (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 .
  3. 1 2 3 Hirota, Kiyoharu; Barnes, Lawrence G. (1994). "A new species of Middle Miocene sperm whale of the genus Scaldicetus (Cetacea; Physeteridae) from Shiga-mura, Japan". Island Arc. 3 (4): 453–472. doi:10.1111/j.1440-1738.1994.tb00125.x.
  4. 1 2 3 4 5 6 Lambert, Olivier; Bianucci, Giovanni; de Muizon, Christian (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 .
  5. 1 2 3 Boersma, Alexandra T. and Pyenson, Nicholas D. (2015). Beatty, Brian Lee (ed.). "Albicetus oxymycterus, a new generic name and redescription of a basal physeteroid (Mammalia, Cetacea) from the Miocene of California, and the evolution of body size in sperm whales". PLOS ONE . 10 (12): e0135551. Bibcode:2015PLoSO..1035551B. doi: 10.1371/journal.pone.0135551 . PMC   4674121 . PMID   26651027.
  6. 1 2 Lambert, Olivier; Bianucci, Giovanni; Beatty, Brian (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.
  7. 1 2 3 4 5 6 Lambert, Olivier; Bianucci, Giovanni; Post, Klaas; de Muizon, Christian; Salas-Gismondi, Rodolfo; Urbina, Mario; Reumer, Jelle (2010). "The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru" (PDF). Nature. 466 (7302): 105–108. Bibcode:2010Natur.466..105L. doi:10.1038/nature09067. PMID   20596020. S2CID   4369352. Archived from the original (PDF) on 2017-12-01.
  8. ↑ Whitehead, Hal (2003). Sperm Whales: Social Evolution in the Ocean. University of Chicago Press. pp. 104–110. ISBN   978-0-226-89517-8.
  9. 1 2 3 Toscano, Antonio; Abad, Manuel; Ruiz, Francisco; Muñiz, Fernando; Álvarez, Genaro; García, Edith Xio-Mara; and Caro, José Antonio (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).
  10. ↑ Fang, Janet (30 June 2010). "Call me Leviathan melvillei". Nature News. doi:10.1038/news.2010.322.
  11. ↑ Ghosh, Pallab (30 June 2010). "'Sea monster' whale fossil unearthed". BBC News. Retrieved 17 July 2024.
  12. ↑ "New Leviathan Whale Was Prehistoric "Jaws"?". National Geographic. 30 June 2010. Archived from the original on July 3, 2010. Retrieved 3 July 2010.
  13. 1 2 Berta, Annalisa (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.
  14. ↑ "Huge Tooth Reveals Prehistoric Moby Dick in Melbourne". Australasian Science Magazine. Retrieved 20 November 2018.
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