page_title: Sanajeh
section_title: Feeding
hierarchical_section_title: Sanajeh / Paleobiology / Feeding
caption_attribution_description: English: A Cretaceous snake Sanajeh indicus feeding on hatchling sauropod dinosaurs. A 3–5-meter-long madtsoiid snake, Sanajeh indicus, waits to feed on hatchling sauropod dinosaurs as they emerge from their eggs, in a scene from the Upper Cretaceous, some 70 million years ago. The sculpture is based on a fossil dinosaur nest from western India, reported in this issue of PLoS Biology [11]. The scales and patterning of the snake's skin is based on modern macrostomatan snakes, relatives of the fossil form. The hatchling dinosaur is reconstructed from known skeletal materials, but its color is conjectural. The eggs are based directly on the fossils. In making their detailed paleobiological interpretations, Wilson and colleagues [11] used all three methods advocated in this review—empirical observations of a remarkable specimen, coupled with comparison with modern analogs and biomechanical modeling. In detail, the authors incorporated museum-based research, field research, stratigraphy and sedimentology, histology, embryology, and use of modern analogs into their interpretation of Sanajeh. (Sculpture by Tyler Keillor and original photography by Ximena Erickson; image modified by Bonnie Miljour). Polski: Kredowy wąż Sanajeh indicus czekający, by zaatakować młodego zauropoda.
context_page_description: Sanajeh is a genus of late Cretaceous madtsoiid snake from western India. A fossil described in 2010 from the Lameta Formation was found coiled around an egg and an adjacent skeleton of a 50 cm long sauropod dinosaur hatchling. This suggests that the snake preyed on hatchling sauropods at nesting sites.
context_section_description: Like many early snakes, Sanajeh did not have the wide gape seen in boids, pythons, and caenophidians. Therefore, it could not consume prey as large as that which many modern snakes can. Living snakes that have narrow gapes, including uropeltids, Anomochilus, Cylindrophis, and Anilius, have diets that are limited to smaller animals such as ants, termite larvae, annelids, and amphisbaenians and caecilians. The short supratemporal and broad, short quadrate indicate that the oral gape of Sanajeh was narrow. The gape is thought to have been similar to that of the extant genus Xenopeltis. However, the presence of strong m. protractor pterygoidei muscles inferred from the sagittal crest of Sanajeh indicates that it was able to manipulate prey in its mouth like modern macrostomatans. The intramandibular joint was able to flex greatly, which would allow for the consumption of larger prey. The presence of these features in Sanajeh shows that increased oral kinesis (movement of the mouth) and intraoral mobility (the ability to move the bones of the palate) preceded the development of wide gapes in snakes. Therefore, reduced cranial kinesis in basal living snakes may be a fossorial adaptation rather than the retention of a plesiomorphic trait. 
  The holotype of Sanajeh was found in association with sauropod eggs belonging to the oospecies Megaloolithus dhoridungriensis and one incompletely preserved sauropod hatchling, likely a titanosaur. The snake was coiled around a crushed egg, which the hatchling may have exited from. The eggs were laid in a nest structure that was not preserved, but was likely covered in loose sediment or vegetation based on the porosity of the eggs. The rigid eggs were probably too large for Sanajeh to consume, but the snake would have been able to break an egg open and consume its contents in a way similar to the living Loxocemus. Sanajeh is likely to have had a nest-plundering feeding strategy, and it is possible that the snake consumed a large variety of prey items including the eggs of theropods and smaller reptiles, which are common in the Lameta Formation.
  Accelerated growth rates and large numbers of hatchlings would have enabled titanosaurs such as Isisaurus and Jainosaurus to overcome the losses of predation by animals such as Sanajeh. Titanosaurs would have been free of the risk of predation by their first year as a result of their rapid growth rate. The size of adult titanosaurs, which could be 20–25 metres (66–82 ft) in length, would have deterred nearly all predators.
caption: A model showing Sanajeh indicus feeding from a titanosaur nest.
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