Theropoda: Coelurosauria

Coelurosauria: Nqwebasaurus, Piveteausaurus, Proceratosaurus, Timimus. Avetheropods closer to birds than to Carnosaurs. Padian et al. (1999). Traditionally, the smaller bipedal carnivores. 

Introduction: "Coelurosauria" has meant a number of different things. Originally it referred to small as opposed to large theropods - everything from Coelophysis to Ornithomimus - but this is now known to be an artificial, polyphyletic grouping group. The popular cladistic meaning is the monophyletic taxon that encompasses all advanced theropods, as well as their descendants the birds (beginning with Archaeopteryx).  The terms Maniraptoria and Maniraptoriformes (refering to the grasping hands of many of these small advanced theropods) are approximately equivalent, but refer to slightly more specialised forms See the next page). (adapted from MAK)

Range: from the Late Triassic? Middle Jurassic? 

Phylogeny: Avetheropoda: Carnosauria + *: Compsognathidae + (Ornitholestes + (Coelurus + Maniraptoriformes)). 

Characters: nasals do not participate in antorbital fossa [H+01]; $ expanded, circular orbit; jugals reach antorbital fenestrae; Fenestra in roof of mouth; $ <16 caudals have transverse processes; "boat-shaped" chevrons; fused sternal plates; "cranial notch" between scapula & coracoid absent [H+01]; coracoid with well-developed posterior projection [H+01]; elongated forelimbs, especially manus [H+01]; semilunate carpal in wrist; metacarpal I reduced; long, thin metacarpal III ; $ ischium reduced to <2/3 length of pubis; $ loss of ischial foot; $ triangular obturator process on ischium; generally femur substantially shorter than epipodialia; $ ascending process of astragalus >25% length of tibia; knee and ankle hinge-like; fibula reduced and immobile in relation to tibia; tarsal bones elongated; metatarsal III pinched between II & IV (arctometatarsalian condition or similar); feathers?. 

Notes: [1] "Coelurosauria" is a name which has been used to describe a number of different groups in this general phylogenetic area at different times. Thus, the dates are uncertain because the definitions used by different authors vary, and also because some of the earlier material is not conclusively identifiable. In these Notes, Coelurosauria is the stem group birds > Allosaurus. [2] Note the many adaptations which may limit maneuverability as they increase speed and stability to impact.  

Image: Coelophysis from DinoData. 

Links: DD: Coelurosauria; Coelurosaurs!; Coelurosauria; Coelurosauria -- The Dinosauricon; theropods; Coelurosauria; DGF, Geological Society of Denmark, Geologisk Tidsskrift Nr. 4, 1996; Basal Coelurosauria; Oudst bekende coelurosaurier (Dutch); Coelurosauria. 

References: Hutt et al. (2001) [H+01].  ATW010517.

Compsognathidae: Compsognathus, Sinosauropteryx(?). 

Range: Late Jurassic-Early Cretaceous. of Eur. 

Phylogeny: Coelurosauria: (Ornitholetes + (Coelurus + Maniraptoriformes)) + *. 

Characters: The following description relates to Compsognathus, as it is not clear what other forms may be contained in the group. About 1m; skull long and low, with sharply tapering snout; lower jaw slender, no coronoid process or external mandibular fenestrae (unusual); very lightly constructed skull , with large openings; paired skull elements not fused; orbit large; pleurocoels only in cervical vertebrae; centra spool-shaped and amphiplatyan; fan-shaped neural spines; no transverse processes on caudals; cervical zygapophyses not flexed; proximal caudal vertebrae long, slender, and somewhat spool-shaped; small curved chevrons; ribs continue to sacrum; cervical ribs double-headed, not fused to vertebrae, taper distally; fine bony gastrula; forelimb about 1/3 length of hind limb; lacks bowed ulna and extended metacarpal III; prominent obturator process on ischium; pes digit I reduced; some forms feathered (if Sinosauropteryx is *); lizard found as stomach contents; presence in Solnhofen indicates * may have been sympatric with Archaeopteryx. 

EHP Crosslinks: DD: Sinosauropteryx 

Links: Compsognathus sp.; Compsognathus Skeleton; Compsognathus Skull; Sino-Dino.jpg. 

Ornitholestes: 

Range: Late Jurassic of NAm (Bone Cabin & ComoBluff). 

Phylogeny: Coelurosauria:: (Coelurus + Maniraptoriformes) + *. 

Characters: Lightly-built, small (2m, 15kg?) carnivore. Small head, but with robust lower jaw; upper & lower jaws curved apart distally; ornamental crest on rostrum; very long (1m) tail, cervical zygapophyses are not elongated; relatively long arms with strong manual unguals; femur length about equal to tibia. 

Image: Ornitholestes from Lectures 17 and 18 - Late Jurassic: Morisson, Tendaguru. 

Links: DD: Ornitholestes; Ornitholestes -- The Dinosauricon; BBC Online - Walking with Dinosaurs - Fact Files; Ornitholestes; jurassic images; Lecture 18 - Late Jurassic: Morisson, Tendaguru; Ornitholestes Printout- ZoomDinosaurs.com; Saurischian dinosaurs: Coelurosaur: Ornitholestes; REFERENCES for ORNITHOLESTES; Ornitholestes (Dutch); Looking at Ornitholestes; An Agile Ornitholestes, 1914; Osborn's Ornitholestes, 1903; Ornitholestes hermanni; Ornitholestes Image Layout 1.  ATW030910.

Coelurus: C. fragilis Marsh 1879.

Range: Late Jurassic (Kimmeridgean) of North America.

Phylogeny: Coelurosauria::: Maniraptoriformes + *.

Characters: ~2m long (all specimens may be subadult); skull shorter & taller than Ornitholestes [M+98]; neck very long [C87]; vertebrae slender, especially cervicals & caudals [C87]; vertebrae and long bones strongly pneumatic [M84]; vertebrae hollow, with large central cavity and thin walls [C87]; cervicals that possess diapophyseal shelves that are broad and curved; anterior cervicals "convexo-concave" (opisthocoelous?), other "bicoelous" (?!) [M84]; cervicals lack hypapophyses (so not maniraptoran?); cervicals coosified with ribs [M84]; dorsal centra are elongate [S88] and spool-shaped; dorsal centra and neural arches laterally compressed [S88]; neural spines much reduced [S88]; relatively low neural arches [S88]; pleurocoel in neural arch divided by vertical septum [S88]; dorsal ribs have undivided heads [S88]; 4 sacral vertebrae [C87]; elongated prezygapophyses in distal caudals & cervicals [M+98]; scapula strap-like [M+98]; humerus much shorter than femur [C87]; ulna bowed [M+98]; manus long & slender [M+98]; semilunate carpal [M+98]; manus I short; manus II & III long, with sharp claws; phalanges elongate [C87]; digits capable of "great flexion and extension" [C87]; laterally compressed unguals [C87]; theropod pelvis (?) [C87]; femur with major trochanter anterior [C87]; below major trochanter is "low, longitudinal ridge-like angle" [C87] (probably lesser trochanter, described as "low & square" in [M+98]); relatively little flexion at knee based on limited antero-posterior extension of femoral condyles [C87]; tibia longer than femur [M+98]; metatarsals very long & slender [M84], with very thin walls [M88].

Note: [1] Phylogenetic position follows Holtz (2001). [2] Seeley (1888) is describing a rather different animal, but repeatedly uses Coelurus as a point of comparison. 

Links: DinoData: Coelurus; Coelurus -- The Dinosauricon; COELURUS; Coelurus (Dutch); Coelurus; Coelurus The Natural History Museum's Dino Directory; Paleontology and Geology Glossary: Co; Saurischian dinosaurs: Coelophysid: Coelurus; MEA592D Dinosaur Osteology: Lecture 6; Coelurus; COELURUS (Spanish); Coeluro (Spanish);  Exotenwelt-Coelurus (German); ????? (Japanese models). 

References: Cope (1887) [C87]; Holtz (2001); Marsh (1884) [M84]; Marsh (1888) [M88]; Miles et al. (1988) [M+98]; Seeley (1888) [S88].  ATW030420.

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