''Mambachiton'' (meaning "crocodile armour") is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus of basal avemetatarsalian from the Middle/ Upper Triassic Makay Formation (Isalo II beds) of Madagascar. The genus contains a single species, ''M. fiandohana'', known from a partial skeleton with articulated

osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amph ...

Discovery and naming

The ''Mambachiton'' fossil specimens were discovered in sediments of the Makay Formation near Sakaraha in the southern Morondava Basin of Madagascar, and excavated later in 1997, 1998, and 2003. The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

specimen, UA 8-25-97-132, consists of an articulated series of cervical vertebrae with associated

s, a cervical rib, and a nearly-complete right postfrontal. An additional referred specimen, FMNH PR 5065, was found near the holotype and includes

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

, sacral, and caudal vertebrae, both scapulocoracoids, the right ilium, and a partial femur. The specimen was first mentioned in a 2019 abstract. In 2023, Nesbitt et al. described ''Mambachiton fiandohana'' as a new genus and species of

avemetatarsalia Avemetatarsalia (meaning "bird metatarsals") is a clade of diapsid Reptile, reptiles containing all archosaurs more closely related to birds than to crocodilians. The two most successful groups of avemetatarsalians were the dinosaurs and pterosau ...

n archosaurs based on these fossil remains. The generic name, "''Mambachiton''", combines the Swahili word "mamba", meaning "crocodile" with the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

"khiton" ("χιτών"), meaning "a suit of armour". The name also references chiton molluscs, as the armour of ''Mambachiton'' superficially resembles that of polyplacophorans. The specific name, "''fiandohana''", is derived from a Malagasy word meaning "source" or "beginning", as ''Mambachiton'' is phylogenetically close to the crocodile-bird split.

Description

''Mambachiton'' was a similar size to the Tanzanian aphanosaur '' Teleocrater'', which was about in body length. Osteoderms were found articulated with the fossilized vertebrae of ''Mambachiton'', including three pairs of osteoderms above each cervical vertebra.

Classification

Nesbitt et al. (2023) recovered ''Mambachiton'' as the earliest diverging member of

Avemetatarsalia Avemetatarsalia (meaning "bird metatarsals") is a clade of diapsid Reptile, reptiles containing all archosaurs more closely related to birds than to crocodilians. The two most successful groups of avemetatarsalians were the dinosaurs and pterosau ...

. They specifically noted that it lacks multiple characters of the minimally inclusive clade containing aphanosaurs and ornithodirans, and is thus nested outside of that clade. Preliminary analyses considered ''Mambachiton'' to be a basal poposauroid (a clade of

pseudosuchia Pseudosuchia, from Ancient Greek ψεύδος (''pseúdos)'', meaning "false", and σούχος (''soúkhos''), meaning "crocodile" is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely relat ...

ns), though the later recognition of aphanosaurs as early-diverging avemetatarsalians corrected this view. The results of the

phylogenetic analyses In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as Computational phylogenetics, phylogenetic inference. It infers the relationship among organ ...

of Nesbit et al. are shown in the

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

below: In the preliminary results of their novel phylogenetic analyses, Garcia & Müller (2025) did not exclude the possibility that ''Mambachiton'' was a member of the Aphanosauria; depending on the analysis constraints, it was recovered within a polytomic Aphanosauria, within a

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

Aphanosauria in a clade including ''Teleocrater'' and '' Spondylosoma'', or as the sister taxon to Dinosauriformes within the

Dinosauromorpha Dinosauromorpha is a clade of avemetatarsalians ( archosaurs closer to birds than to crocodilians) that includes the Dinosauria (dinosaurs) and some of their close relatives. It was originally defined to include dinosauriforms and lagerpetids ...

Paleoenvironment

''Mambachiton'' was discovered in layers of Isalo II, also referred to as the Makay Formation, which dates to the Middle/Late

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

period ( Ladinian–

Carnian The Carnian (less commonly, Karnian) is the lowermost stage (stratigraphy), stage of the Upper Triassic series (stratigraphy), Series (or earliest age (geology), age of the Late Triassic Epoch (reference date), Epoch). It lasted from 237 to 227.3 ...

ages), though the exact numerical age is currently unknown. The traversodontids '' Menadon'' and '' Dadadon'', the rhynchosaur '' Isalorhynchus'', and the lagerpetid '' Kongonaphon'' have also been described from the type locality, as well as the remains of unnamed reptiles,

synapsids Synapsida is a diverse group of tetrapod vertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida (which includes all extant rept ...

, and possibly amphibians.

References

{{Taxonbar, from=Q120968248 Avemetatarsalia Ladinian life Carnian life Middle Triassic archosaurs Late Triassic archosaurs Middle Triassic reptiles of Africa Late Triassic reptiles of Africa Triassic Madagascar Fossils of Madagascar Prehistoric reptile genera Fossil taxa described in 2023