Yerrapalli Formation

Yerrapalli Formation Stratigraphic range: Middle Triassic (Anisian)
Type	Geological formation
Underlies	Bhimaram Formation
Overlies	Kamthi Formation
Thickness	600 metres (2,000 ft)
Lithology
Primary	Mudstone, sandstone, caliche
Location
Region	Pranhita–Godavari Basin
Country	India
Type section
Named for	Yerrapalli village
Named by	Jain et al., 1964

The Yerrapalli Formation is a Triassic rock formation consisting primarily of mudstones that outcrops in the Pranhita–Godavari Basin in southeastern India. The Yerrapalli Formation preserves fossils of freshwater and terrestrial vertebrates as well as trace fossils of invertebrates. The tetrapod fauna includes temnospondyl amphibians, archosauromorph reptiles, and dicynodonts.

Geology

Most of the Yerrapalli Formation consists of red mudstones. The mudstones were deposited across a floodplain during the Anisian stage of the Middle Triassic. Smaller lenses of calcareous sandstone represent ephemeral streams that branched off from the larger channels that were the source of the floodplain sediments. The climate of the region during the time is thought to have been monsoonal with both wet and dry seasons.

The Yerrapalli Formation overlies the Kamthi Formation, underlies the Bhimaram Formation, and is conformable with both formations. Two members of the Yerrapalli Formation have been recognized; a lower member consisting of layers of red and purple clay with lenses of pale green clay and an upper member consisting of alternating layers of clay and fine-grained sandstone.

Paleobiota

The paleobiota of the Yerrapalli Formation is similar to that of the overlying Maleri Formation, which also preserves fossils of temnospondyls and archosauromorphs. The main difference between the Yerrapalli and the Maleri faunae is the presence of dicynodonts in the former. The discovery of dicynodont fossils in the Pranhita-Godavari Basin in 1964 was one of the earliest indications that the Yerrapalli Formation represented a distinct paleofauna. Before this discovery, Yerrapalli strata were grouped within the Maleri Formation. The dicynodonts of the Yerrapalli Formation are similar to those of the Ntavere Formation in Zambia, which also dates back to the Anisian. During the Middle Triassic, what is now India and southern Africa formed one continuous landmass as part of the supercontinent Gondwana.

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Fishes

Taxon	Material	Notes	Images
Ceratodus sp.		A lungfish
Saurichthyidae sp.		A chondrostean ray-finned fish

Amphibians

Taxon	Material	Notes	Images
"Parotosuchus" rajareddyi		A capitosaurid temnospondyl first referred to Parotosuchus but more recently considered either a species of Eryosuchus or of Stanocephalosaurus

Reptiles

Taxon	Material	Notes	Images
Erythrosuchidae indet.		A possible erythrosuchid archosauriform
Mesodapedon kuttyi	Two specimens including skull bones	A rhynchosaur similar to Stenaulorhynchus stockleyi from the Manda Formation of Tanzania, which is the same age as the Yerrapalli Formation
Pamelaria dolichotrachela	One complete skeleton, one partial skeleton, and isolated bones	A long-necked prolacertid archosauromorph	150px
Yarasuchus deccanensis	An articulated, nearly complete skeleton and a partial disarticulated skeleton	A long-necked poposauroid pseudosuchian	150px

Synapsids

Taxon	Material	Notes	Images
Rechnisaurus cristarhynchus	A mostly complete skull	A kannemeyeriiform dicynodont
Trirachodontidae indet.	Isolated teeth
Wadiasaurus indicus		A kannemeyeriiform dicynodont