| Titanotaria | |
|---|---|
 | |
| Holotype skull ofTitanotaria orangensis | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Carnivora |
| Clade: | Pinnipedia |
| Family: | Odobenidae |
| Genus: | †Titanotaria Magallaneset al., 2018 |
| Species: | †T. orangensis |
| Binomial name | |
| †Titanotaria orangensis Magallaneset al., 2018 | |
Titanotaria is a genus of late, basalwalrus from the Miocene ofOrange County, California. Unlike much later odobenids, it lacked tusks.Titanotaria is known from an almost complete specimen which serves as the holotype for the only recognized species,Titanotaria orangensis, it is the best preserved fossil walrus currently known.
Although the holotype specimen (OCPC 11141) ofTitanotaria had been discovered in 1993 and represents one of the most complete fossil walrus known, little attention was given to the material for over 20 years. The first mention of the fossils in peer-reviewed literature came in 2017 with Barboza and colleagues[1] publishing a faunal list of the Oso Member of theCapistrano Formation, whereTitanotaria had been found. Specifically, the fossilized bones were collected from the town ofLake Forest,Orange County, California, during the construction of theSaddleback Church.[2] A full description followed a year after its mention by Barboza and was led by Isaac Magallanes, who published a detail examination of the fossils alongside a phylogenetic analysis.[3] According to paleontologist Robert Boessenecker, the remains were unofficially known by the name "Waldo".[4]
The nameTitanotaria honors theCalifornia State University, Fullerton, widely known as the Titans. This was meant to recognize the collaboration between the university and Orange County, which lead to the creation of theJohn D. Cooper Archaeological and Paleontological Center. The second part of the genus name, otaria, is a reference to the genusOtaria and a commonly usedsuffix for fossil pinnipeds. The species name means "coming from Orange County".[3]
The holotype skull ofTitanotaria belongs to a male individual with an asymmetric skull, likely caused by a healed pathology. The rostrum ofTitanotaria is elongated and widens at around the root of the firstcanine tooth. Thepremaxilla are triangular in outline and elevated slightly above the tooth row. The front-most tip of the premaxilla is marked by a knob-shaped prenarial process, which is immediately followed by a depression located above the incisors and canines that likely serves as an origin for the lateralnasalis muscle. Thenasal bones are long (60% of the rostrum length) with parallel edges and a broad, V-shaped suture with thefrontal bone. Thezygomatic arch is broad and possesses an oval prominence on its ventral surface. The point of articulation between the jugal and the maxilla is largely fused and a small, triangular postorbital process is present on the jugal element of the zygomatic arch. Thefrontal bone is widest towards the front of the skull and bears two temporal crests, which fuse to form thesagittal crest. The crest is prominent and long, with a sinuous profile. This differs from the more sloping sagittal crests of other odobenids likeImagotaria andNeotherium. Towards the back of the skull the sagitall crest meets the nuchal crests, which is wide and obscures theoccipital region in top view.[3]
The tooth formula ofTitanotaria is. In the upper jaw the incisors are long and slender with an oval crosssection and a single root. The canines are robust, conical and larger than the incisors. While the firstpremolar likely only possesses a single root based on the morphology of the alveolous, the second is bi-lobed with a bulbous tooth crown. The following teeth also show two tooth roots and there is a decrease in size between the twomolars. No incisors are preserved in the lower jaw and their alveoli are obscured by sediment. The mandibular tooth row is very short, only taking up 40% of the mandible. The lower canines are almost as large as their upper counterparts and like them they are robust and conical with a curve to them. Like in the upper jaw, the teeth starting with the second premolar of the mandible are double rooted with bulbous crowns. The last lower molar however appears to have been single rooted based on the anatomy of its tooth socket.[3]
Titanotaria preserves most of its postcranial material; however, only elements relevant to phylogenetic analysis were described. The holotype is only missing few ribs, parts of the right forelimb, most of thepelvis and some of the distal limb elements.[3] It reached a length of 10 ft (3.0 m) and weighed around 1,200 lb (540 kg).[2]
Phylogenetic analysis found thatTitanotaria was a basal odobenid, nesting outside of the cladeNeodobenia (named within the same publication as the genus).[3] The same placement was later recovered by Biewer and colleagues when they describedOsodobenus.[5]
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Titanotaria is known from the Oso Member of theCapistrano Formation, which preserves a rich assemblage of fossil walrus species such asGomphotaria pugnax,Pontolis magnus,Pontolis kohnoi andOsodobenus eodon. Theeared sealThalassoleon was also found in this formation, alongsidegiant sea cows,cetotheriid whales, the bizarreDesmostylus, various sharks and the remains of indetermined crocodiles.[1][5][3]
