Toyotamaphimeia
Toyotamaphimeia | |
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Toyotamaphimeia machikanensis skeleton | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Clade: | Archosauromorpha |
Clade: | Archosauriformes |
Order: | Crocodilia |
Family: | Gavialidae |
Subfamily: | Gavialinae |
Genus: | †Toyotamaphimeia Aoki, 1983 |
Type species | |
†Tomistoma machikanense Kobatake et al., 1965
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Species | |
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Synonyms | |
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Toyotamaphimeia (named after
History and naming
The first bones belonging to Toyotamaphimeia were discovered on May 3, 1964, during the construction of a new school building on the grounds of Ôsaka University. A field survey was conducted shortly afterwards, confirming the presence of more fossils, however not yet identifying their crocodilian nature. Following the survey several digs were organized starting on 9 June 1964. The skull was found on September 17 during the second dig. A third excavation was held in December which yielded more material of Toyotamaphimeia as well as fossil shellfish, insects and plant remains. Finally a fourth excavation took place in January 1965. Following analysis of the fossils, the material was assigned to the genus Tomistoma and named Tomistoma machikanense.[4] In 1983, 18 years after the initial discovery, the skull was redescribed and deemed different enough from Tomistoma to erect a new genus, Toyotamaphimeia creating the comb. nov. Toyotamaphimeia machikanensis. In turn, Aoki also changed the species name from machikanense to machikanensis, as the new genus name was feminine.[5] Similar remains were also known from Taiwan and had been classified as Tomistoma taiwanicus and Toyotamaphimeia sp. respectively, the former of which suggested as a species of Toyotamaphimeia already in 1983.[5] A 2023 study concluded that both belonged to a single taxon: the Taiwanese form retained the species name, but was placed in Toyotamaphimeia, creating the new combination T. taiwanicus.[1]
The generic name derives from Toyotama-hime, a goddess of Japanese mythology with the ability to change her appearance to that of a crocodile.[5] The species epithet of T. machikanensis means "from Mountain Machikane" ((ja:待兼山)), while that of T. taiwanicus derives from Taiwan.[4]
Description
The
Toyotamaphimeia's skull is triangular in shape and longirostrine. It's fairly large, measuring over 1 metre (3.3 ft) from the tip of the premaxillary to the posterior end of the parietal. Most of that length is taken up by the maxilla and the nasal bones penetrate the premaxilla dorsally, extending deep into the premaxilla to the level of the 3rd maxillary alveoli, but not coming in contact with the nares. The skulltable of the holotype is crushed and damaged just before the orbits. The dentaries are broken off at the anterior end and each preserves 10 alveoli. The absence of any grooves or confluence of alveoli suggests that the specimen is mature, which is consistent with its great size.[6][8]
Paleobiology
The holotype specimen (MOUF00001) preserves a series of pathologies described by Katsura in 2004. The mandible is broken off at the tip, the tibia and fibula have been fractured and healed and some of the osteoderms present preserve healing bite marks. The fact that these injuries healed is evidence that the animal survived for a while after being injured and Katsura suggests that they may have been the result of intraspecific fights, furthermore hypothesizing that this could mean the Osaka University specimen may have been a male.[8]
Although the holotype of Toyotamaphimeia is the first substantial and best preserved evidence of crocodilians in Japan, there are other remains found across the islands. The northernmost finds were made in the Iwate Prefecture (northern
Phylogeny
Below is a cladogram based morphological studies comparing skeletal features that shows Toyotamaphimeia as a member of Tomistominae, related to the false gharial:[2]
Crocodylidae
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Based on morphological studies of
The phylogenetic trees of Iijima et al. (2022) as well as Cho and Tsai (2023) are featured below.
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References
- ^ .
- ^ ISSN 0031-0182.
- ^ "Valuable Specimen which Osaka University Possesses". Archived from the original on 2005-03-06.
- ^ .
- ^ S2CID 87351884.
- ^ a b c Kobayashi, Y.; Tomida, Y.; Kamei, T.; Eguchi, T. (2006). ""Anatomy of a Japanese tomistomine crocodylian, Toyotamaphimeia machikanensis (Kamei et Matsumoto, 1965), from the middle Pleistocene of Osaka Prefecture: the reassessment of its phylogenetic status within Crocodylia"". National Science Museum Monographs (35).
- PMC 7891683.
- ^ S2CID 84758037.
- ^ Taruno, H. (1999). "A fossil crocodile from Nagareki Town, Kishiwada City". Excavation Report on a Fossil Crocodile from Nagareki Town, Kishiwada City: 1–36.
- ^ Brochu, C.A.; Gingerich, P.D. (2000). "New tomistomine crocodylian from the Middle Eocene (Bartonian) of Wadi Hitan, Fayum Province, Egypt". University of Michigan Contributions from the Museum of Paleontology. 30 (10): 251–268.
- PMID 12775527.
- PMID 12775528.
- PMID 17433721.
- PMID 18372192.
- PMID 22431965.
- PMID 30051855.
- PMID 33907305.
- PMC 8905159.
External links
- Media related to Toyotamaphimeia at Wikimedia Commons
- Data related to Toyotamaphimeia at Wikispecies