Kuttysuchus

{{Short description|Genus of reptile}} {{Speciesbox | fossil_range = [[Late Triassic]] {{fossilrange|Norian|Rhaetian}} | image = | image_caption = | taxon = Kuttysuchus minori | parent_authority = Haldar, Ray & Bandyopadhyay, 2025 | authority = Haldar, Ray & Bandyopadhyay, 2025 }}

'''''Kuttysuchus''''' is an extinct genus of [[Typothoracinae|typothoracine]] [[aetosaur]] from the [[Late Triassic]] [[Lower Dharmaram Formation|Dharmaram Formation]] of [[India]]. It was described in 2025 on the basis of multiple isolated osteoderms that were nonetheless distinct in their appearance from not only the contemporary ''[[Venkatasuchus]]'' but also from other aetosaur taxa. The specific combination of characters suggests that ''Kuttysuchus'' was a member of the clade [[Paratypothoracini]], with phylogenetic analysis indicating it to have been a basal member of the group. The genus is [[monotypic]], only containing a single species. '''''Kuttysuchus minori'''''.

==History and naming== ''Kuttysuchus'' was described in early 2025 on the basis of a series of isolated paramedian [[osteoderms]], with one almost complete bone serving as the [[holotype]]. All fossils stem from the [[sandstone]]-dominated lower unit of the [[Dharmaram Formation]], located in the [[Pranhita–Godavari Basin]] of eastern India and thought to date from the mid or late [[Norian]] to the [[Rhaetian]] stages of the [[Triassic]].<ref name=HRB25>{{Cite journal |last1=Haldar |first1=A. |last2=Ray |first2=S. |last3=Bandyopadhyay |first3=S. |year=2024 |title=A new paratypothoracin aetosaur (Archosauria: Pseudosuchia) from the Upper Triassic Dharmaram Formation of India and its biostratigraphic implications |journal=Journal of Vertebrate Paleontology |volume=44 |issue=3 |at=e2439533 |doi=10.1080/02724634.2024.2439533 |bibcode=2024JVPal..44E9533H }}</ref>

''Kuttysuchus'' was named after Tharavat S. Kutty, who recovered the fossil material. The second part of the name derives from the Greek "suchus", which translates to "crocodile". The species name "minori" meanwhile references the small size of the osteoderms.<ref name=HRB25/>

==Description== The only fossils found of ''Kuttysuchus'' are paramedian osteoderms, which form the much wider central two rows of armor that would have stretched across the animal's back in life. The smaller, triangular lateral osteoderms that would have attached to the side of the paramedian osteoderms have not been found. As with other aetosaurs, the paramedian osteoderms are wider than they are long, however, in this particular case the width:length radio is relatively low, with the width being less than twice the length. This, coupled with the strong transverse flexure of the osteoderms and some other features suggest that they formed the anterior or middle tail armor. Overall the osteoderms are rather thin, unlike those of desmatosuchins.<ref name=HRB25/>

The front of each osteoderm forms the unornamented (smooth) anterior bar, which in articulation would slide beneath the previous osteoderm. In ''Kuttysuchus'', the anterior bar is weakly raised. The medial edge of the anterior bar, meaning the one directed towards the midline of the animal, bears a short and pointed spur that is not as well developed as in some other taxa like ''[[Stagonolepis]]''. Just before this projection the anterior bar thins slightly, which is known as scalloping. The inner (medial) edge of the osteoderms is straight and thin, the ancestral condition among aetosaurs, lacking the thickened articular surface that is characteristic of desmatosuchins.<ref name=HRB25/>

The osteoderms bear a prominent dorsal eminence, a pyramid-shaped raised region that in ''Kuttysuchus'' is located much closer to the back edge of the osteoderm yet not touching the actual posterior margin, something that is a shared trait among paratypothoracins. Additionally, the dorsal eminence is described as mediolaterally elongated, meaning it is stretched in width. The shape of the eminence does help differentiate ''Kuttysuchus'' from other species, which may variable exhibit spike-like, bulbous knob-like, mound-like or even keel-like dorsal eminences, but is close in shape to that of ''[[Typothorax]]'' and ''[[Paratypothorax]]''. However it is noted that the shape of the dorsal eminence varies based on the position of the osteoderm, with those closer to the tail being often more strongly developed before reducing in size again around the mid-caudal region. Unlike in the contemporary ''Venkatasuchus'', the eminence in ''Kuttysuchus'' did not connect to a ridge, nor was the back edge of the osteoderm bevelled as in the former. The dorsal eminence forms somewhat of a center for the ornamentation of the osteoderm and various sharp, straight ridges as well as deep narrow grooves radiate outwards from the element, with small pits filling the spaces between them. Notably, the grooves do not contain any pits themselves, which sets them apart from those of ''[[Venkatasuchus]]'', the other Dharmaram aetosaur. The ornamentation coupled with the shape of the dorsal eminence distinguish ''Kuttysuchus'' from members of [[Desmatosuchini]], though they do bear some resemblance to non-desmatosuchin stagonolepoid aetosaurs.<ref name=HRB25/>

The lower (ventral) surface of the osteoderms is smooth, lacing the pits and ridges that ornament the dorsal surface. Each osteoderm bears a prominent convex region that bears a weakly developed thickening, the so-called ventral strut. At the position of the dorsal eminence, the osteoderms arch or flex.<ref name=HRB25/>

==Phylogeny== Though the lack of complete paramedian and lateral osteoderms can cause issues in phylogenetic analysis, Haldar, Ray and Bandyopadhyay have argued that the osteoderm armor of ''Kuttysuchus'' is complete and distinct enough to be used in order to determine the animals relationships within [[Aetosauria]]. Two analysis were run by the team, one based on the work of Haldar ''et al.'' (2023) and another based on Reyes ''et al.'' (2024), with the latter including the wildcard taxon ''[[Garzapelta]]'', noted by Haldar and colleagues to be an example of an aetosaur whose incomplete nature causes conflicting phylogenetic positions.<ref name=HRB25/>

Following resampling, the first analysis recovers ''Kuttysuchus'' as the earliest branching member of the Paratypothoracini, with the contemporary ''Venkatasuchus'' in a much more derived position within the group. Nevertheless, this topology is well supported by the study, meaning that it is likely that ''Kuttysuchus'' was a paratypothoracin. Though not as well resolved as the first analysis, the second phylogenetic analysis, which included ''Garzapelta'', recovered similar results. It too placed ''Kuttysuchus'' at the base of Paratypothoracini, in this scenario in a polytomy with ''[[Kocurypelta]]''. Here too the contemporary ''Venkatasuchus'' was found to be nested much deeper in the clade. Cladograms based on both analysis are shown below, the left following iteration 1 based on the dataset of Haldar ''et al.'' (2023) and the right following iteration 2 based on the dataset of Reyes ''et al.'' (2024).<ref name=HRB25/>

{|- valign="top" | align="left" width="50%" | {{clade| style=font-size:85%;line-height:85% |label1=Aetosauria |1={{clade |1=''[[Aetosauroides]]'' |2={{clade |1=[[Stagonolepidoidea]] |label2=Aetosaurinae |2={{clade |1={{clade |1=''[[Aetosaurus]]'' |2=''[[Coahomasuchus]]'' }} |label2=Typothoracinae |2={{clade |1=''[[Apachesuchus]]'' |2={{clade |1=''[[Typothorax]]'' |2=''[[Redondasuchus]]'' }} |label3=Paratypothoracini |3={{clade |1='''''Kuttysuchus''''' |2={{clade |1=''[[Rioarribasuchus]]'' |2={{clade |1=''[[Kocurypelta]]'' |2={{clade |1=''[[Venkatasuchus]]'' |2={{clade |1=''[[Tecovasuchus]]'' |2=''[[Paratypothorax]]'' }}}}}}}}}}}}}}}}}}}} | align="left" width="50%"| {{clade| style=font-size:85%;line-height:85% |label1=Aetosauria |1={{clade |1=''[[Aetosauroides]]'' |2={{clade |1=''[[Stenomyti]]'' |2=[[Stagonolepidoidea]] |label3=Aetosaurinae |3={{clade |1={{clade |1=''[[Aetosaurus]]'' |2=''[[Coahomasuchus]]'' }} |label2=Typothoracinae |2={{clade |1=''[[Apachesuchus]]'' |2={{clade |1=''[[Typothorax]]'' |2=''[[Redondasuchus]]'' }} |label3=Paratypothoracini |3={{clade |1='''''Kuttysuchus''''' |2=''[[Kocurypelta]]'' |3={{clade |1=''[[Rioarribasuchus]]'' |2={{clade |1=''[[Venkatasuchus]]'' |2={{clade |1=''[[Tecovasuchus]]'' |2=''[[Paratypothorax]]'' }}}}}}}}}}}}}}}}}} | align="right" width="50%" | |}

==Paleobiology== The fauna of the lower Dharmaram Formation is dominated by archosaurs, which in addition to ''Kuttysuchus'' included a [[phytosaur]] of the clade [[Mystriosuchinae]], several [[sauropodomorphs]] including ''[[Jaklapallisaurus]]'' and even a [[neotheropod]]. At least two other aetosaurs are known from these sediments, one undescribed taxon similar to ''[[Desmatosuchus]]'' as well as the paratypothoracin ''[[Venkatasuchus]]''. The presence of paratypothoracins has been used in previous studies to suggest that the lower Dharmaram Formation could be as old as the middle Norian.<ref name=HRB25/>

==References== {{Reflist}}

[[Category:Late Triassic pseudosuchians]] [[Category:Prehistoric pseudosuchian genera]] [[Category:Fossil taxa described in 2025]] [[Category:Aetosauria]]