Ornitholestes hermanni
Creators: name: Osborn, H. F.
Publisher: name: Zenodo
Year: 1917
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Reptilia
Dinosauria
Compsognathidae
Ornitholestes
Ornitholestes hermanni

description: RESTUDY OF <i>ORNITHOLESTES HERMANNI</i> OSBORN. Text-figs. 1-3, Plate XXVI. The original <i>reconstruction</i> of the skeleton (Osborn, 1903, fig. 1, p. 460)1 is <i>very</i> inaccurate. It was based partly upon Marsh’s restoration of the skeleton of <i>Anchisaurus.</i> The cervical ribs are incorrectly restored; the presacral vertebrae, restored as twenty-eight, are certainly too numerous; the digits of the manus (Osborn, 1903, figs. 1, 2, 3) are restored as spreading instead of closely appressed; the skull is incorrectly drawn. The following characters may be pointed out in the new reconstruction shown in Plate <b>XXVI</b>, which is based upon a restudy of the type specimen (Amer. Mus. No. 619) supplemented by the manus of the second specimen (Amer. Mus. No. 587). <i>Vertebral formula.</i> The vertebral formula is uncertain; it is estimated in comparison with that of other Theropoda as follows: It will be observed that there <i>is</i> a constant number of twenty-three pre-sacrals in <i> Struthiomimus, Allosaurus, <i>2</i> and <i>Tyrannosaurus,</i> which renders it probable that <i>Ornitholestes</i> also had not more than twenty-three pre-sacrals.</i> The boundary line between the cervical and thoracic vertebrae in the American Museum skeleton of <i>Ornitholestes</i> is uncertain because the two vertebrae C9 and C10 are missing, but in <i>Struthiomimus,</i> in which the cervical series is complete, the boundary line is clearly indicated by the change in the character of the ribs from the fixed, coalesced condition (C10) to the movable bicipital condition (Th. 1). <i>Skull.</i> (1) Teeth: premaxillary 4, maxillary 10; crowns not so serrate or prehensile as in typical carnivorous dinosaurs. (2) Cranium with two antorbital openings, prominent premaxillaries, typical theropod <i>arrangement</i> of lachrymals, <b>frontals</b>, postorbitals, parietals, squamosals, <b>quadratojugals</b>, opisthotics. (<b>3) Dentary</b> with twelve small upright or slightly <i>recurved</i> teeth. (4) <b>Jaw</b> with sessile coronoid process. <b>1</b> Osborn, H. F. <b>“</b> Ornitholestes hermanni, <b>a</b> New Compsognathoid Dinosaur from the Upper Jurassic. <b>”</b> Bull. <i>Amer</i>. Mus. Nat. Hist., Vol. XIX, <i>Art</i>. xii, July 23, 1903, pp. 459 <b>—</b> 164. <b>2</b> In the National Museum series of <i>Allosaurus</i> there were found <i>nine</i> cervicals, fourteen dorsals, and five sacrals; there were two <b>breaks</b> in the series, but evidently the whole number was present. <i>Letter</i> of C. W. Gilmore, <i>January</i> 8, 1916. <i>Vertebrae.</i> Cervicals nine or ten in number, gently opisthocoelous; dorsals amphicoelous; caudals amphicoelous. The supposed 7th and 8th cervicals are moderately elongate, slightly <i>opisthocoelous</i>, with separate attachments for the capitulum of <b>a</b> freely articulated rib on the anterior portion of the centrum and for the tuberculum on the broad diapophysial extension of the neural arch. The <i>neuro-central</i> suture is faintly indicated. It appears that the cervical ribs were slender, free, and two-headed in <i>Ornitholestes</i> while in <i>Struthiomimus</i> they are firmly coalesced with the sides of the cervical centra and arches, <b>a</b> progressive character. For other details of the vertebrae see original description (Osborn, 1903, p. 460). Four firmly coalesced sacral ribs are suturally distinct. Caudals 39- 44e, anterior caudal ribs coalesced. The very characteristic rod-like elongation of the zygapophyses of the caudal vertebrae begins with the vertebra supposed to be C13; it reaches its maximum between C16 and C24. In these vertebrae the chevrons are depressed, elongate, bifurcated in front, with <b>a</b> posterior keel. In <i>Struthiomimus</i> the rod-like elongation of the prezygapophyses begins with C12 and reaches the maximum in C26-C30, which are so rigidly articulated by the elongate zygapophyses and chevrons as to admit of little or no movement. <i>Pelvic girdle.</i> <b>The</b> pelvic <b>girdle</b> is broadly similar in contour to that of <i>Struthiomimus,</i> but ilium, pubes, and ischia are suturally separate, while in <i>Struthiomimus</i> they are firmly coalesced; pubes with deep symphysial union; ischia more slender, with proximal anterior processes united distally; peduncle of pubes missing in the type. <i>Hind limb.</i> Femur (.207m.) and tibia (.159m.) estimated to be of unequal length, the femur being the longest bone. In <i>Struthiomimus</i> the tibia is more elongate, a cursorial adaptation. The pes tridactyl; median metatarsal, Mts. III (.117 m.), relatively less elongate than <i>in Struthiomimus:</i> condition of Mts. V unknown. The total length of the hind limb <i>is</i>.483 m., the tibio-femoral ratio is.706, which indicates that the movement of this animal was not so swift as that of <i>Struthiomimus (Ornithomimus), in</i> which the. tibio-femoral ratio is: 1.11 (T.540-F. 480). It appears from the preserved terminal phalanges that they were <i>more</i> recurved and clawlike than <i>in Struthiomimus (Ornithomimus).</i> <i>Fore limb.</i> In the fore limb of <i>Ornitholestes</i> the humerus is somewhat longer (.127 m.) than the ulno-radius, which is also the proportion observed in <i>Struthiomimus.</i> In the figures accompanying the original description of <i>O. hermanni</i> (Amer. Mus. 587, see Figs. 7A, 7B, p. 748) the proportions are correctly represented. We observe a marked anisodactyly and lateral compression of the manus (Figs. 2, 3 B). Mtc. II is enlarged and greatly elongate while Mtc. III is reduced and abbreviated, and Mtc. IV is vestigial; Digit I is partly known in the type as being short and somewhat divergent (<i>Plate</i> XXVI); Mtc. I and Ph. I. 2 only are preserved. This manus may, therefore, be described as functionally <i>anisotetradactyl</i> whereas that of <i>Struthiomimus</i> is comparatively <i>isotridactyl,</i> indicating a very marked difference in habit. In other words, the manus of <i>Ornitholestes</i> while subraptorial is more highly reduced than that of <i>Struthiomimus.</i> The central digits are closely appressed to each other (as in <i>Struthiomimus)</i> while the claws are relatively more powerful and recurved (Fig. 7B) than in <i>Struthiomimus.</i> The <i>Ornitholestes</i> manus is losing its fitness as a raptorial grasping type, it is too <i>feeble</i> and too much reduced; it represents a species adaptation to another purpose, recalling in some features the slender and greatly elongated digits of the Aye- Aye <i>(Cheiromys).</i> In (Fig. 3) <i>Ornitholestes, Struthiomimus,</i> and the manus associated with <i>Ornithomimus</i> (Fig. 3 <i>a</i>) metatarsal I is closely appressed to metatarsal II. The phalanges of the pollex are divergent and rotated inwards in the two genera first named, <i>Ornitholestes</i> and <i>Struthiomimus.</i> The fact that the central digits of <i>Ornitholestes</i> are closely appressed and incapable of spreading laterally harmonizes with the incipient coalescence of Mtc. I and Mtc. II in <i>Struthiomimus.</i> Another harmony is the divergence of the phalanges of Digit I.
description: Published as part of <i>Osborn, H. F., 1917, Skeletal Adaptations of Ornitholestes, Struthiomimus, Tyrannosaurus, pp. 733-771 in Bulletin of the American Museum of Natural History 35</i> on pages 735-738, DOI: 10.5281/zenodo.1040385
description: {"references": ["Osborn, Henry Fairfield. \" Ornitholestes hermanni, a New Compsognathoid Dinosaur from the Upper Jurassic. \" Bull. Amer. Mus. Nat. Hist., Vol. xix, Art. xii, July 23, 1903, pp. 459 - 464."]}