Incertovenator

Source: Wikipedia, the free encyclopedia.

Incertovenator
Temporal range:
Ma
↓
Axis and third cervical of the holotype of Incertovenator (PVSJ 397)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauromorpha
Clade: Archosauriformes
Clade:
Eucrocopoda
Clade: Archosauria (?)
Genus: †Incertovenator
Yáñez et al., 2021
Species:
†I. longicollum
Binomial name
†Incertovenator longicollum
Yáñez et al., 2021

Incertovenator (meaning "uncertain hunter") is an

pseudosuchians. The type and only known species is I. longicollum, which is known from single specimen discovered in the Late Triassic (Carnian aged) Ischigualasto Formation of Argentina. Incertovenator is known almost entirely by its vertebral column. This indicates that it had a relatively long neck, leading to its uncertain classification due to the convergent evolution of elongated neck vertebrae in both avemetatarsalian and pseudosuchian archosaurs.[1]

Discovery and naming

Map of the type locality of PVSJ 397 within the Ischigualasto Formation.

The

stratigraphically positioned at roughly mid-level in the Cancha de Bochas member, approximately 120 metres (390 ft) above the base of the Ischigualasto Formation. The specimen was formally described in 2021 by Imanol Yáñez, Diego Pol, Juan Martín Leardi, Oscar A. Alcober, and Ricardo N. Martínez, and is held in the Museo de Ciencias Naturales at the National University of San Juan, Argentina.[1]

The specimen is almost entirely known by its vertebral column (

haematite coating and permineralization. Additionally, the deformation has distorted the shape of the vertebrae and parts of them have been cracked and weathered away.[1]

The

generic name comes from the Latin words incerto- (uncertain) and venator (hunter), referencing its uncertain phylogenetic relationships to other archosaurs and its presumed predatory lifestyle. Likewise, the specific name is from Latin longus and collum, meaning "long neck", in recognition of its notably elongated cervical vertebrae.[1]

Description

Articulated dorsal vertebrae of Incertovenator

As it is known almost entirely from vertebrae, little can be confidently said about the life appearance of Incertovenator, apart from it having a relatively long neck. However, it was likely a quadruped, similar to the majority of other early-diverging archosaurs, including potential relatives (aphanosaurs and early-diverging loricatans).

The axial skeleton of Incertovenator is well-known, with vertebrae from all the major regions of the spine (cervicals, dorsals, sacrals and caudals) as well as associated

neural spines are similarly longer than high, and overhang each centrum at the front with tips that are expanded and rugosely textured.[1]

The dorsal vertebrae are shorter than the cervicals, but are still relatively long compared with other archosaurs; their centra are both longer than they are tall, and taller than wide. Unlike the cervicals, they lack a keel on their underside and have no hollowed out fossae on their surfaces. The neural spines, however, are similar to the cervicals' in that they are long and low, roughly similar in height to the centra. This trait is unusual for aphanosaurs, but similar to some dinosauromorphs, crocodylomorphs and Mandasuchus.[1]

Incertovenator has only two sacral vertebrae, the ancestral condition for archosaurs, and they are unfused. Their neural spines are low, like the dorsals, although the first sacral spine has a slight forward slant and the second resembles that of the axis, with an arched upper margin. The caudal centra are also longer than they are high, although they gradually become shorter moving down the tail. The neural spines are also similar to those of the dorsals, although they shift from a roughly central position from the first caudal towards the back of the centrum by the fifth caudal.[1]

Sacral and first six caudal vertebrae of Incertovenator

The only other known part of the skeleton is the

poposauroids and most crocodylomorphs.[1]

Classification

When introduced to a dataset of Triassic

aphanosaurs mid-cervicals longer than its mid-dorsals, cervical neural spines with expanded tips and a roughened texture, dorsal neural spines with expanded, rounded tips, and cervical neural spines that slant forwards at their front edge (a trait previously interpreted as an unambiguous synapomorphy of aphanosaurs). Alternatively, a position in Pseudosuchia related to Mandasuchus is supported by sharing a convex dorsal margin of the axial neural spine and a forward slant to the front face of their cervicals.[1]

The cladogram below is reproduced and simplified from Yáñez et al., 2021:

Ilium of Incertovenator, note the relatively long preacetabular process.
Archosauria
 

Additional suboptimal positions were also identified on the cladogram, including as the sister taxon to

proterochampsid Tropidosuchus. Some of these positions were also associated with the elongation of the cervicals, although notably the shape of the ilium is similar to early crocodylomorphs, derived poposauroids, pterosaurs and dinosaurs, namely the long preacetabular process. These conflicting signals cloud its relationship to other archosaurs even further.[1]

Palaeoecology

As indicated by its name, Incertovenator was presumed to be a predator, largely due to the convergent evolution of similar long-necks being associated with small-sized predatory archosaurs.

cynodonts Chiniquodon, Diegocanis, Ecteninion, and Exaeretodon.[2]

References

  1. ^
    S2CID 239239894
    .
  2. S2CID 37918101
    .
Retrieved from "https://en.wikipedia.org/w/index.php?title=Incertovenator&oldid=1183951665"