SPS 100/44

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SPS 100/44 is the accession number given to a fossil of an unnamed genus of troodontid dinosaur discovered in Mongolia. In the scientific literature it is referred to as the "EK troodontid", after the Early Cretaceous sediments in which it was found.


SPS 100/44 was discovered by S.M. Kurzanov during the 1979 Soviet-Mongolian Paleontological Expedition. It was found in deposits of the Barunbayaskaya Svita at the Khamareen Us locality, Dornogov (southeastern Gobi Desert), in the Mongolian People's Republic.


SPS 100/44 was described by Rinchen Barsbold and colleagues in 1987.[1] Its fossil remains include an incomplete skeleton consisting of the braincase, posterior parts of the lower mandibles, a maxillary fragment with teeth, parts of five cervical vertebrae, an articulated right manus with partial semilunate, left manus phalanx I-1, distal end of the left femur, and fragmentary left and right pedes. Barsbold pointed out that the specimen was smaller and from older sediments than other known troodontids, but it had some features of the skull that could have made it a juvenile. Barsbold also indicated the high degree of fusion of the bones of the skull and the unusual foot morphology to indicate that it might be an adult of an unknown taxon. Barsbold took the conservative position and did not name this specimen because it was not complete enough to rule out the possibility that it was a juvenile of a known genus of troodontid.

Barsbold also noted that the naturally articulated manus of SPS 100/44 showed no signs of an opposable third digit, as was suggested for Troodon by Russell and Seguin in 1982.

Turner and colleagues, in 2007, found the EK troodontid to be a distinct basal genus of troodontid, in a polytomy with Jinfengopteryx and a clade of more derived troodontids.[2] See Troodontidae.

See also[edit]


  1. ^ Barsbold, Rhinchen, Osmolska, Halszka, Kurzanov, S.M. (1987). "On a new troodontid (Dinosauria. Theropoda) from the Early Cretaceous of Mongolia". Acta Palaeontologica Polonica 32(1-2): 121-132
  2. ^ Turner, Alan H.; Pol, Diego; Clarke, Julia A.; Erickson, Gregory M.; and Norell, Mark (2007) "A basal dromaeosaurid and size evolution preceding avian flight" http://www.sciencemag.org/cgi/reprint/317/5843/1378.pdf "Science" 317:1378-1381 doi=10.1126/science.1144066