Tristychius

Tristychius (from Greek: τρεις treis, 'three' and Greek: στῐ́χος stíkhos 'row')[2] is an extinct genus of elasmobranch chondrichthyan from the Carboniferous period (Visean). Fossils of T. arcuatus, the type and only species, including fin spines have been found in Scotland.

Tristychius Temporal range: Early Carboniferous,
Restoration of Tristychius
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Order:	†Hybodontiformes
Family:	†Tristychiidae
Genus:	†Tristychius Agassiz, 1837[1]
Type species
†Tristychius arcuatus Agassiz, 1837

Tristychius was a small animal, up to about 60 centimetres (2 ft) long. It had a heterocercal caudal fin, and large spines on two dorsal fins.[3] Unlike other chondrichthyans that have three basal plates on pectoral fin (propterygium, mesopterygium and metapterygium), its pectoral fin had only two basal plates and lacked mesopterygium.[4] Even through it is one of the earliest known stem-elasmobranchs, it is estimated to be a specialized suction feedeeing benthic predator, either ambushing or using stealth to approach its prey.[5]