G. V. R. Prasad

Cosmopolitanism among Gondwanan Late Cretaceous mammals

Consistent with geophysical evidence for the breaking up of Pangaea, it has been hypothesized that Cretaceous vertebrates on progressively isolated landmasses exhibit generally increasing levels of provincialism, with distinctly heightened endemism occurring at the beginning of the Late Cretaceous. The Cretaceous fossil record from the southern supercontinent of Gondwana has been much too poor to test this hypothesis with regards to mammals (Fig. 1 ). Early Cretaceous mammals are known only from isolated sites in Argentina, Australia,, Cameroon, and Morocco. Apart from several occurrences in South America, knowledge of Late Cretaceous Gondwanan mammals is limited to a single site in India that previously yielded a few specimens of placental mammals,, and a site in Madagascar that previously yielded only one indeterminate tooth fragment. Here we report the occurrence of a highly specialized and distinctive group of extinct mammals, the Sudamericidae (Gondwanatheria), in the Late Cretaceous of Madagascar and India. These new records comprise the first evidence of gondwanatheres outside South America and the first indication of cosmopolitanism among Late Cretaceous Gondwanan mammals. Antarctica may have served as an important Cretaceous biogeographic link between South America and Indo-Madagascar.

Cretaceous Extinctions: Multiple Causes

![Figure][1] Deccan plateau basalts. Lava from Deccan volcanism formed distinct layering. CREDIT: GSFC/NASA In the Review “The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene boundary” (P. Schulte et al. , 5 March, p. [1214][2]), the terminal Cretaceous

Fossil lizards from the Jurassic Kota Formation of India

Abstract The Mesozoic lizard fauna of Gondwana is virtually unknown. We report here on a lizard assemblage from the Upper Member of the Kota Formation of peninsular India, usually considered to be of Early–Middle Jurassic age. The dominant form, Bharatagama rebbanensis, gen. et sp. nov., has a predominantly acrodont dentition. Comparison with living and extinct taxa suggests that this new genus is a primitive acrodont iguanian distinct from the Cretaceous priscagamids. It predates known records of iguanian lizards by some 80 Ma, and provides evidence that iguanians had begun to diversify before the break-up of Pangea. A second fully pleurodont taxon is known from the same deposit. It is tentatively attributed to the Squamata but is too fragmentary for further determination.

A radiation of arboreal basal eutherian mammals beginning in the Late Cretaceous of India

Indias Late Cretaceous fossil mammals include the only undisputed pre-Tertiary Gondwanan eutherians, such as Deccanolestes. Recent studies have suggested a relationship between Deccanolestes and African and European Paleocene adapisoriculids, which have been variably identified as stem euarchontans, stem primates, lipotyphlan insectivores, or afrosoricids. Support for a close relationship between Deccanolestes and any of these placental mammal clades would be unique in representing a confirmed Mesozoic record of a placental mammal. However, some paleogeographic reconstructions place India at its peak isolation from all other continents during the latest Cretaceous, complicating reconstructions of the biogeographic history of the placental radiation. Recent fieldwork in India has recovered dozens of better-preserved specimens of Cretaceous eutherians, including several new species. Here, we incorporate these new specimens into an extensive phylogenetic analysis that includes every clade with a previously hypothesized relationship to Deccanolestes. Our results support a robust relationship between Deccanolestes and Paleocene adapisoriculids, but do not support a close affinity between these taxa and any placental clade, demonstrating that Deccanolestes is not a Cretaceous placental mammal and reinforcing the sizeable gap between molecular and fossil divergence time estimates for the placental mammal radiation. Instead, our expanded data push Adapisoriculidae, including Deccanolestes, into a much more basal position than in earlier analyses, strengthening hypotheses that scansoriality and arboreality were prevalent early in eutherian evolution. This comprehensive phylogeny indicates that faunal exchange occurred between India, Africa, and Europe in the Late Cretaceous-Early Paleocene, and suggests a previously unrecognized ∼30 to 45 Myr “ghost lineage” for these Gondwanan eutherians.

Cretaceous age for Ir‐rich Deccan intertrappean deposits: palaeontological evidence from Anjar, western India

Micropalaeontological investigations of an iridium‐bearing, lacustrine intertrappean sedimentary sequence at the western margin of the Deccan volcanic province near Anjar, have revealed a profuse occurrence of theropod eggshell fragments (ornithoid type) in beds overlying the iridium‐enriched levels. Associated late Cretaceous ostracods, lack of evidence of reworking, and the absence of any exclusively Palaeocene taxa above the iridium levels, taken together, indicate that the extinction of dinosaurs in the Indian subcontinent occurred after the deposition of Ir layers at Anjar, and that these Ir anomalies may significantly predate the K–T boundary.

Implications of the infra- and inter-trappean biota from the Deccan, India, for the role of volcanism in Cretaceous-Tertiary boundary extinctions

The fossil record shows a remarkable similarity between the biota that existed before and after the initiation of Deccan volcanic activity. Virtually all the available palaeontological evidence, such as the fauna and flora of the freshwater infra- and inter-trappean beds and the planktonic foraminifera from the subsurface infra- and inter-trappean beds of the southeastern coast, do not favour the initiation of Deccan volcanism as the cause of mass extinctions at the Cretaceous-Tertiary (K-T) boundary. Instead, a combination of events, such as an extended period of volcanism, changes in sea-level and related climatic changes, and certain local factors, may have played a significant role in selectively eliminating various groups of organisms. This view is further reinforced by the biotic changes across the K-T iridium layer in the Um Sohryngkew River section of Meghalaya, northeastern India.

Taphonomy of a late Cretaceous mammal-bearing microvertebrate assemblage from the Deccan inter-trappean beds of Naskal, peninsular India

Abstract Taphonomic analysis of a microvertebrate assemblage from the late Cretaceous Deccan inter-trappean sequence of Naskal, peninsular India, is undertaken to infer the taphonomic factors involved in the accumulation of bones at a time predaceous avians and large mammals were non-existent. Approximately 1 ton of matrix was screen washed and a large number (> 9100) of isolated skeletal remains of fish, amphibians, turtles, lizards, snakes, crocodiles, mammals and dinosaurs, in addition to pelecypods, ostracodes, gastropods and charophytes were recovered. Different mechanisms are postulated for the initial accumulation of the fauna. Whereas scavenging activity played no significant role in the accumulations, hydraulic sorting was responsible for accumulation of the terrestrial and semi-aquatic component of the fauna. The wide distribution of bone fragments, presence of pre-burial fractures on some of the bones and the occurrence of the assemblage in a thin, calcareous palaeosol unit indicate that the vertebrate remains accumulated rapidly as a consequence of a prolonged, drought-induced, mass mortality event and were subjected to subaerial exposure. The study concludes that the Naskal assemblage accumulated in a distal floodplain lake, which served as a natural death trap, on whose banks terrestrial and other animals might have gathered in search of food and water during a prolonged drought and perished subsequently due to the desiccation of the lake.

The first multituberculate mammal from India

Mesozoic deposits of the former Gondwanaland are depauperate in early mammals, in general, and multituberculate mammals, in particular. Until now, the oldest multituberculate mammals known from the Gondwanan continents come from the Early Cretaceous of Morocco, NW Africa. Here, we report the presence of a new multituberculate mammal, Indobaatar zofiae gen. et sp. nov., from the Lower/Middle Jurassic Kota Formation, Pranhita-Godavari valley in peninsular India. This is the first record of a multituberculate from the Mesozoic rocks of India and possibly predates the oldest known multituberculates from Gondwanan continents. The new specimen, representing an upper premolar (P4), compares well with the upper premolar morphology of Eobaatariinae multituberculates known from the Early Cretaceous of Mongolia, China, England, and Spain. Together with the recent findings of cimolodontan multituberculates from the Early Cretaceous of Australia and Late Cretaceous of South America, the new discovery indicates a wide temporal and spatial distribution for multituberculate mammals in the former Gondwanaland.

A NEW LATE CRETACEOUS VERTEBRATE FAUNA FROM THE CAUVERY BASIN, SOUTH INDIA: IMPLICATIONS FOR GONDWANAN PALEOBIOGEOGRAPHY

ABSTRACT Late Cretaceous vertebrate faunas of India are known predominantly from intertrappean deposits in the Deccan volcanic province of the central and western parts of the country. A thick and nearly continuous sequence of Early Cretaceous—Early Paleocene fossiliferous sediments exposed in the Cauvery Basin of South India has been comparatively poorly explored. Here, we present a preliminary description of a new fauna consisting of vertebrate fossils discovered from the continental Upper Cretaceous (late Maastrichtian) Kallamedu Formation. The Kallamedu Fauna includes ganoid fishes, amphibians, turtles, crocodiles, and dinosaurs, with many taxa suggesting Late Cretaceous biotic links between India and other Gondwanan landmasses. Teeth of abelisaurid dinosaurs, known previously from the Middle Jurassic of South America and the Late Cretaceous of Africa, Madagascar, and central and western India, support a pan-Gondwanan distribution for this group oftheropod dinosaurs. Of greatest significance, however, is the first discovery of a Simosuchus-like notosuchian crocodile outside of Madagascar. This report of the first Indian Simosuchus-like notosuchian crocodile further strengthens earlier evidence from other vertebrate groups for close biotic links between India and Madagascar in the Late Cretaceous, most likely through dispersal via the Seychelles block, Amirante Ridge, and Providence Bank.

Amphibians and squamates from the Neogene Siwalik beds of Jammu and Kashmir, India

The Neogene Siwalik deposits of Jammu Province (India) have yielded amphibians and squamates. The collection includes the first amphibians and the first colubroid snakes from the Siwalik Group. Amphibians comprise only anurans: a possible Ranidae and one, or perhaps two, non-ranid frogs Squamates include one lizard,Varanus sp. (Varanidae), whereas snakes are represented by three taxa:Acrochordus dehmi (Acrochordidae), an indeterminate Colubridae, and a snake that is either a Colubridae or an Elapidae.Varanus sp. andA. dehmi have been yielded by the Upper Miocene Ramnagar Member, whereas the anurans and colubroid snakes come from the Upper Pliocene Labli Member. These taxa are indicative of aquatic palaeoenvironment.