Baisesaurus

Baisesaurus (meaning "Baise lizard") is an extinct genus of ichthyosauromorph reptiles from the early Triassic (Spathian age) Luolou Formation of Guangxi, China. The genus contains a single species, Baisesaurus robustus, known from a partial postcranial skeleton.

Baisesaurus Temporal range: Early Triassic, late Spathian[1] PreꞒ Ꞓ O S D C P T J K Pg N ↓
Holotype specimen
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	†Ichthyosauromorpha
Genus:	†Baisesaurus Ren et al., 2022
Species:	†B. robustus
Binomial name
†Baisesaurus robustus Ren et al., 2022

Discovery and naming

The Baisesaurus holotype specimen, CUGW VH107, was discovered in 2018 in a layer of the Luolou Formation (Triassospathodus symmetricus–T. homeri conodont assemblage zones^[1]) in the Nanpanjiang Basin of Zhebao Township in Baise, China. The specimen consists of assorted ribs, gastralia, a limb element (likely a radius), twelve vertebral centra, and seven neural arches.^[2]

In 2022, Ren et al. described Baisesaurus robustus, a new genus and species of basal ichthyosauromorphs. The generic name, "Baisesaurus", combines a reference to the type locality in Baise, China, with the Greek "saurus", meaning "lizard". The specific name, "robustus", means "robust".^[2]

Description and classification

Baisesaurus was likely at least 3 m (9.8 ft) long. It was more similar to Utatsusaurus than to any other ichthyosauromorph, with similar size and anatomical traits. It can be inferred from related animals that Baisesaurus was a strong swimmer with long, compact forelimb bones.^[2]

Baisesaurus likely represents a basal member of the clade Ichthyosauromorpha, albeit outside of the clades Hupehsuchia or Nasorostra. In their 2022 description, Ren and colleagues explained that it may more precisely represent a member of the Ichthyopterygia, but such a classification is highly tentative.^[2]