| Atopotarus Temporal range: | |
|---|---|
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| Holotype skeleton of Atopotarus courseni at the Natural History Museum of Los Angeles County | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Carnivora |
| Clade: | Pinnipedia |
| Family: | †Desmatophocidae |
| Genus: | †Atopotarus Downs, 1956 |
| Species | |
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Atopotarus is an extinct genus of pinniped from the middle Miocene known from one specimen (holotype LACM 1376) from Los Angeles County, California. It belongs to the extinct family Desmatophocidae, an early lineage of seal-like pinnipeds from the North Pacific.[1]
It is a monotypic genus, with the only known species being Atopotarus courseni, or commonly referred to as 'Coursen's Strange Seal.' The species name 'courseni' is attributed to the Coursen family that discovered the fossil in 1952 on their Palos Verdes residence.[2] It is currently on display at the Natural History Museum of Los Angeles County.[3]
The specimen was discovered in the rocks of the Altamira Shale of the Monterey Formation.[4]
Description
The only specimen of Atopotarus is an incomplete articulated skeleton preserved in a slab of rock, with material from the skull to part of the spine, ending before the pelvis. It includes the skull, most teeth, jaws, cervical vertebrae, ribs, some dorsal vertebrae, and elements of the forelimbs, with outlines of the carpals and metacarpals.[2]
As with other members of its family, Atopotarus possessed large orbits, which would indicate that they relied heavily on eyesight for hunting, and may have been deep divers.[5]
Both Atopotarus and modern eared seals share similarly long and well developed neck structures, which is used to allow flexible movements for hunting prey underwater and swimming. It also possessed unusually strong canines and thick jaws, indicating a strong bite force.[2]
While no modern descendants of this genus exist today, they may have been most ecologically similar to elephant seals, due to similarities in eye size that indicate deep-diving hunting strategies.[5]
Taxonomy
Atopotarus can be distinguished from other desmatophocids based on differences in the skull and teeth. Notable differences in the skull include an elongated cranium with large crests, lack of a pre-narial shelf, and the elongated mastoid process, where neck muscles attach and blood vessels flow through, which protrudes ventral to level of the postglenoid process. Differences in the teeth include double rooted premolars as opposed to the single rooted premolars of related genera, smaller canines, and the lack of a second molar.[4]
Atopotarus courseni has been sometimes considered to be a species within Allodesmus, but most recent phylogenetic analysis retains it as a separate genus and a sister taxon to Allodesmus.[1]
References
- 1 2 Boessenecker, Robert W; Churchill, Morgan (2018-09-01). "The last of the desmatophocid seals: a new species of Allodesmus from the upper Miocene of Washington, USA, and a revision of the taxonomy of Desmatophocidae". Zoological Journal of the Linnean Society. 184 (1): 211–235. doi:10.1093/zoolinnean/zlx098. ISSN 0024-4082.
- 1 2 3 Downs, Theodore (1956). "A New Pinniped from the Miocene of Southern California: With Remarks on the Otariidae". Journal of Paleontology. 30 (1): 115–131. ISSN 0022-3360. JSTOR 1300386.
- ↑ Kurland, Zoe (2022-05-06). "This Exhibit Lets You Tour LA — When It Was Underwater And Populated With Giant Sea Creatures". LAist. Retrieved 2023-08-29.
- 1 2 Barnes, Lawrence G.; Hirota, Kiyoharu (1994). "Miocene pinnipeds of the otariid subfamily Allodesminae in the North Pacific Ocean: Systematics and relationships". The Island Arc. 3 (4): 329–360. doi:10.1111/j.1440-1738.1994.tb00119.x. ISSN 1038-4871.
- 1 2 Debey, Lauren B.; Pyenson, Nicholas D. (2012-03-21). "Osteological correlates and phylogenetic analysis of deep diving in living and extinct pinnipeds: What good are big eyes?". Marine Mammal Science. 29 (1): 48–83. doi:10.1111/j.1748-7692.2011.00545.x. ISSN 0824-0469.