Eostrix is a genus of extinct primitive owls in the family Protostrigidae, along with Oligostrix and Minerva. These owls date from early Eocene of the United States, Europe, and Mongolia. They have been described based on fossil remains. The genus was created by Pierce Brodkorb in 1971 to place a fossil species known until that time as Protostrix mimica.
Temporal range: early Eocene
E. mimica (Wetmore, 1938)
The following species are recognised:
- E. mimica described in 1938 by Alexander Wetmore using hindlimb elements in Eocene strata in Wyoming.
- E. martinellii was described in 1972 from a left tarsometatarsus (lower leg bone) recovered from an escarpment above the southeastern bank of Cottonwood Creek in Fremont County, Wyoming by Jorge Martinelli on a field trip in 1970 under the auspices of the University of Kansas. The strata was a Lysite member of the Wind River Formation. Martinelli was studying paleontology at the University of Barcelona. Paleontologists Larry D. Martin and Craig Call Black from the University of Kansas Natural History Museum named it in his honour. The smaller of the two species, it was similar in size to the living long-eared owl (Asio otus). Differences in the trochleas (grooves) of the lower end of the tarsometatarsus set it apart from living owls, namely a groove in the trochlea for digit 2, a deeper posterior groove in a relatively narrow trochlea for digit 3, and an unusually rounded trochlea for digit 4.
- E. vincenti described in 1980 by Colin Harrison from the early Eocene London Clay in England, known from pedal phalanx and proximal tarsometatarsus bones. Some scholars think E. vincenti resembles Necrobyas more than Eostrix.
- E. tsaganica described in 2011 by Evgeny Kurochkin and Gareth J. Dyke, found in Mongolia.
- E. gulottai described in 2016 by Gerald Mayr, found in the early Eocene Nanjemoy Formation in Virginia alongside a dozen other species of birds. This species is the smallest known fossil (or living) owl, with a distal width of 3.9 mm. The structure of its trochlea metatarsi II, a bone in the owl's foot, strongly indicates that it would have restricted the rotation of the second toe. Since a similar bone structure has been observed on birds with webbed feet, this detail has led to the conclusion that the E. gulottai also had webbed feet. Named for the finder of the holotype, Marco Gulotta.
- Mayr, Gerald (2009). Paleogene Fossil Birds. Springer-Verlag Berlin Heidelberg. p. 164. doi:10.1007/978-3-540-89628-9. ISBN 978-3-540-89628-9.
- Martin, Larry D.; Black, Craig C. (1972). "A new owl from the Eocene of Wyoming" (PDF). Auk. 89 (4): 887–88. doi:10.2307/4084122. Retrieved 3 November 2010.
- Harrison, C. J. O. (1980). "A small owl from the Lower Eocene of Britain". Tertiary Research. 3 (2): 83–87. ISSN 0308-9649.
- Kurochkin, E. N.; Dyke, G. J. (2011). "The first fossil owls (Aves: Strigiformes) from the Paleogene of Asia and a review of the fossil record of Strigiformes". Paleontological Journal. 45 (4): 445–458. doi:10.1134/S003103011104006X.
- Mayr, Gerald (2016). "The world's smallest owl, the earliest unambiguous charadriiform bird, and other avian remains from the early Eocene Nanjemoy Formation of Virginia (USA)" (PDF). PalZ. 90 (4): 747–763. doi:10.1007/s12542-016-0330-8.
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