''Liolithax'' is an extinct genus of
dolphin
A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the ...
from the
Middle Miocene
The Middle Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene.
The sub-epoch lasted from 15.97 ± 0.05 Ma to 11.608 ± 0.005 Ma (million y ...
(
Serravallian
The Serravallian is, in the geologic timescale, an List of time periods, age or a stage (stratigraphy), stage in the middle Miocene epoch (geology), Epoch/series (stratigraphy), Series, which spans the time between 13.82 annum, Ma and 11.63 Ma (m ...
)
Temblor Formation
The Temblor Formation is a geologic formation in California. It preserves fossils dating back from the Late Oligocene to the Middle Miocene of the Neogene period. It is notable for the famous Sharktooth Hill deposit (otherwise known as Ernst Q ...
of California.
Taxonomy
''Liolithax kernensis'', described by
Remington Kellogg on the basis of the periotic CAS 4370 in 1931, was considered the only species of the genus until Barnes (1978) reassigned ''"
Lophocetus" pappus'' to ''Liolithax'' based on similarities between the holotype periotic of ''L. kernensis'' and the periotic of ''L. pappus''. ''Liolithax'' was grouped in Kampholophinae with ''
Kampholophos'' by Barnes (1978, 1985).
The discovery of a skull from middle Miocene deposits in Baja California, Mexico cast doubt on the congenericity of ''"Lophocetus" pappus'' with the ''Liolithax'' type species by including a petrosal more similar to ''L. kernensis'' than to the petrosals included in the skulls of ''pappus''. In a 2008 SVPCA abstract, Lawrence Barnes and colleagues noted that the Baja California skull differed from ''"Lophocetus" pappus'' in having a smaller tooth diameter, a more slender rostrum, and smaller size. They classified ''Liolithax'' in Kentriodontinae while stressing that ''"Lophocetus" pappus'' is a lophocetine in need of a new generic name. The cladistic analysis of ''
Brujadelphis
''Brujadelphis'' is an extinct genus of river dolphin-like cetaceans of uncertain family placement from the Late Miocene epoch (Serravallian) of present-day Peru. The type species is ''Brujadelphis ankylorostris'', recovered from the Pisco Forma ...
'' by Lambert et al. (2017) recovered ''"Lophocetus" pappus'' (as ''Liolithax pappus'') as sister to
Lipotidae
Lipotidae is a family of river dolphins containing the possibly extinct baiji of China and the fossil genus ''Parapontoporia'' from the Late Miocene and Pliocene of the Pacific coast of North America. The genus '' Prolipotes'', which is based on ...
, but did not test the phylogenetic relationships of ''Liolithax kernensis'' relative to Lipotidae, Iniidae, or other kentriodontids.
[Olivier Lambert, Giovanni Bianucci, Mario Urbina, Jonathan H. Geisler; A new inioid (Cetacea, Odontoceti, Delphinida) from the Miocene of Peru and the origin of modern dolphin and porpoise families. Zool J Linn Soc 2017; 179 (4): 919-946. doi: 10.1111/zoj.12479. https://academic.oup.com/zoolinnean/article/179/4/919/3076080/A-new-inioid-Cetacea-Odontoceti-Delphinida-from?guestAccessKey=3b956b95-d215-488a-8d90-1cff59554290#63703008] It is therefore possible that ''"Lophocetus" pappus'' could be an early relative of the
baiji
The baiji (; IPA: ; ''Lipotes vexillifer'', ''Lipotes'' meaning "left behind" and ''vexillifer'' "flag bearer") is a possibly extinct species of freshwater dolphin native to the Yangtze river system in China. It is thought to be the first dolph ...
.
References
{{Taxonbar, from=Q48996447
Miocene cetaceans
Miocene mammals of North America
Fossil taxa described in 1931