Coelurosauria: Tyrannosauroidea: Tyrannosaurinae

Taxa on this Page

1. Albertosaurus X  
2. Gorgosaurus X   
3. Tyrannosaurinae X  
4. Tyrannosaurini X  

Descriptions

Tyrannosaurinae: Alioramus, Shanshanosaurus

Range: Late Cretaceous (Campanian to Maastrichtian) of East Asia & North America

Phylogeny: Tyrannosauridae: Alectrosaurus + * : (Albertosaurus + Gorgosaurus) + Tyrannosaurini.

Characters: nasals rugose [$H01a]; frontals with posterior end laterally expanded [$H01a]; supratemporal fossa occupies posterolateral half of frontal [$H01a]; lateral nuchal crest formed by parietals present, at least twice as tall as foramen magnum vertical height; pair of tab-like processes on supraoccipital wedge; basisphenoidal sphenoidal sinus deep, with large foramina; vomers fused, with anterior portion expanded to greater than twice shaft width; palatine dorsal surface without prominent muscular fossae; supradentary fused to coronoid, restricting lateral motion of intramandibular joint; premaxillary teeth serrated [C00]; premaxillary tooth row more mediolaterally than anteroposteriorly oriented; maxillary tooth count <17 [C00]; maxillary & dentary teeth wide & tall [C00]; distal caudal neural spines axially elongate; acromial expansion well-developed, more than twice scapula midshaft width "acromial expansion"?); scapula contributes more than half of the glenoid; scapular-humerus ratio between 2.2 and 2.5; metacarpal III very reduced and bears no digit; ilium long, slight shorter than femur; ilium with horizontal medial shelf from preacetabular blade to sacral ribs; ilium preacetabular blade with broad ventral hook-like projection; ilium with pronounced midline crest; supraacetabular crest on ilium reduced; pubic boot enlarged, approximately one-half pubis length; Ischium shaft long but more slender and shorter than pubis.

Notes: what appear to be group death assemblages are known for both Albertosaurus and Tyrannosaurus, particularly the former. This suggests that tyrannosaurines were at least sometimes gregarious. [C97].

Image: typical laterally expanded incisiform premaxillary tooth from a Japanese site.

Links: DinoData Classification Tyrannosaurinae; Further review of the tyrannosaurids; Tyrannosaurid Systematics; Untitled Document Japanese); TYRANNOSAURIDAE German).

References: Currie (1997a) [C97]; Currie (2000) [C00]; Holtz (2001a) [H01a]. ATW021212.

Albertosaurus:  A. sarcophagus Osborn 1905.

Range: Late Cretaceous (Early Maastrichtian) of North America (Alberta) [H01a].

Phylogeny: Tyrannosaurinae:: Gorgosaurus + *.

Characters: 7.5-9.0m; premaxilla very broad & short; pro-maxillary fenestra well in front of the maxillary fenestra; maxillary fenestra higher than long; maxillary fenestra separated from antorbital fenestra by a thin bar of maxilla; moderate lacrimal horn; lacrimal horn oriented dorsally [$?H01a]; lacrimal horn anterior to descending ramus of lacrimal [$?H01a]; suborbital prong of postorbital prominent [$?H01a]; suborbital prong of postorbital anterior margin jagged [$H01a]; "orientation of occipital region caudoventral" [$H01a]; basal tubera reduced [$H01a]; basisphenoid foramina in sphenoidal sinus each lie in separate fossa [$H01a]; 2+ foramina on ventral surface of palatine [$?H01a]; ventral pocket of ectopterygoid chamber strongly reduced [$?H01a]; small surangular foramen; strong, forwardly inflected scapular blade; distal end of scapula expanded to more than twice midshaft width [$H01a] [CS01]; deltopectoral crest relatively large (reversal) [$H01a]; gracile tibia; femur to tibia length ratio over 1.0.

Image: right) from CM Studio (left) adapted from Michael Corriss.

Links: DinoData Dinosaurs A050 ALBERTOSAURUS; Albertosaurus1 carefully watch the quicktime movie & ask yourself whether you buy this sequence for a 2500 kg animal); Albertosaurus- Enchanted Learning Software good discussion of the running problem); Albertosaurus; Albertosaurus ?????????; Dino Land Travels Database Field Museum- Albertosaurus; ALBERTOSAURUS; Morales Albertosaurus; Albertosaurus sarcophagus; Spotlight on Albertosaurus; Albertosaurus; Dinosaurios- Albertosaurio; Albertosaurus; Albertosaurus & Therapods; Wanted- Albertosaurus @ nationalgeographic.com; Albertosaurus; DinoNews.net - Le dinosaure Albertosaurus.     

References: Carpenter & Smith (2001) [CS01]; Holtz (2001a) [H01a]. ATW030302.

Gorgosaurus:  G. libratus Lambe 1914. May be a junior synonym of Albertosaurus, but the weight of current opinion is that the original designation of a separate genus was correct.

Range: Late Cretaceous (Late Campanian) of North America (Alberta). [H01a], [L17].

Phylogeny: Tyrannosaurinae:: Albertosaurus + *.

Characters: up to 9m; Cranial: head narrow & moderately elongate [L17]; maxilla ventral margin "irregularly undulating" [L17]; nasal suture to frontal with lateral projections extending more posteriorly than medial projections [$?H01a]; promaxillary fenestra close to the maxillary fenestra; promaxillary fenestra anterodorsal to maxillary fenestra in adults [$H01a]; maxillary fenestra oval and separated from the antorbital fenestra by a wide bar of the maxilla; lacrimal horn anterior to descending ramus of lacrimal [H$?01a]; postorbital contacts lacrimal below orbit [$?H01a]; ventral pocket of ectopterygoid chamber strongly reduced [$?H01a]; Mandibular:surangular foramen present [L17]; Dental: 4 premaxillary teeth [L17]; premaxillary teeth typical tyrannosaurid (D-shaped, carinae, etc.) [L17]; 13 maxillary and 14 dentary teeth [L17]; first maxillary tooth incisiform [$?H01a] [L17]; other lateral teeth with anterior and posterior carinae (carinae serrated over entire length) laterally expanded [L17]; teeth replaced alternately, with new teeth arising medially, then displacing old root [L17]; Axial: vertebrae slight amphicoelous [L17]; vertebrae concave both laterally and ventrally [L17]; 11 dorsals, 5 sacrals & ~34 caudals [L17];  neural spines short [L17]; cervical neural spines excavated front & back, positioned posteriorly on centrum [L17]; cervical zygapophyses on robust processes [L17]; parapophyses directed posteroventrally from below prezygapophysis base [L17]; cervical ribs double-headed [L17]; posterior cervical ribs greatly elongated with large thin base and long complexly curved distal extremity (see image above) [L17]; dorsal diapophyses broad, well up on arch, directed dorsolaterally & somewhat posteriorly [L17]; dorsal diapophyses reinforced by thickened lamina of bone [L17]; dorsal neural spines increase length towards sacrum [L17]; dorsal neural spines extended anteriorly & posteriorly with medial lamina which may fuse to adjoining spine [L17]; dorsal vertebrae medial laminae terminally rugose, with numerous foramina & channels (ligaments?) [L17]; thoracic ribs double-headed, long & robust [L17]; thoracic rib heads straight & axially flattened between vertebral attachments [L17]; long, robust gastralia, distally elongated with "supplementaries" [L17]; gastralia meeting and overlapping on the ventral midline [L17]; gastralia continuous with thoracic ribs, forming almost unbroken band around entire abdomen [L17]; tail about half total length [L17]; caudal vertebrae with transverse processes ending with 14th caudal [L17]; distal caudals strongly interlocked with  greatly elongated prezygapophyses [L17] [3]; chevrons intervertebral, with shape changing radically in distal vertebrae as shown in the image [L17]; distally, caudal centra lengthen, ventral concavity increases, prezygapophyses elongate, spines become lower [L17]; Forelimb: scapula strap-like & expanded at both ends [L17]; scapula acromial process very deep; coracoid plays relatively minor role in glenoid [CS01] [L17]; glenoid long, relatively narrow, with strong anterior rim [L17] but poorly developed medial wall [CS01]; glenoid rectangular [CS01]; notch in lateral margin of glenoid along scapula-coracoid suture [CS01]; coracoid thin, broad & roughly rectangular [L17]; forelimbs very small, ~25% length of hindlimb [L17]; humerus twice length of ulna [L17]; proximal humerus posteriorly concave [L17]; ulna triangular in cross section proximally [L17]; "stout olecranon process" [L17] [5]; radius somewhat rectangular in cross-section [L17]; 5 carpals, all small, rounded, flattened & relatively featureless [L17]; vestigial Mc III present [L17]; Mc I very short [L17]; metacarpal distal articular surface consisting of simple groove [L17]; manus phalangeal formula 23000, including unguals [L17]; phalanx I1 with twist along long axis [CS01]; phalanx I1 same length as McII [$H01a]; phalanx I2 much longer [L17];  Hindlimb: robust [L17]; ilium elongate, plate-like, with flat dorsal surface in lateral view and rounded ends [L17]; ilium longer anterior to acetabulum than posterior [L17]; pubic peduncle and region above acetabulum particularly massive [L17];  dorsal margin of ilium, both lateral & medial surfaces heavily marked by muscle attachments [L17]; pubis expanded posteriorly for broad articulation with ischium [L17]; pubic symphysis (not fused) at about 1/2 shaft length [L17]; large pubic foot, extending further posteriorly than anteriorly [L17]; prominent muscle scar on dorsal surface of ischial shaft [L17]; ischial foot absent [L17]; femur and tibia about same length [L17]; femoral head well set off from shaft [L17] [6]; greater trochanter continuous with head, but separated from lesser trochanter by deep groove [L17]; lesser & 4th trochanter both well-developed [L17]; tibia relatively robust; tibia angles forward distally [L17]; tibia with heavy muscular attachment process on proximal,  anteromedial surface [L17]; large cnemial process on anterolateral surface [L17]; fibula small, with proximal expansion [L17]; astragalus with very broad ascending process [L17]; metatarsals long, with Mt III 2/3rds as long as tibia [L17]; arctometatarsus present [L17]; pes phalangeal formula 23450 [L17].

Notes: [1] There is considerable confusion about this taxon. For most of its history, it was treated as a junior synonym of Albertosaurus. Currently, it is treated as a separate genus. However, it is uncertain whether Gorgosaurus and Albertosaurus make up a clade, or whether they are separate branches from the main line of tyrannosaur evolution [H01a].  One of the difficulties is that most of the skull of the holotype was crushed and useless. [2] Lambe's original description in 1914 identified the manual digits as II & III (actually I & II). He corrects this error in his 1917 description. [3] Note how tightly the caudals would have been locked together, particularly in the distal tail. The distal half of the tail was probably a rigid, rod-like structure, held together not only by the tight zygapophyseal articulations, but by the beveled edges of the centra and the "stapling" effect of the intervertebral chevrons. Likely the tail could not have been dragged on the ground, even if the animal had wished to do so.  [4] Another remarkable feature is the continuous abdominal armor of gastralia plus thoracic ribs. At least anteriorly, Gorgosaurus was almost literally barrel-chested, with the entire anterior abdomen and sides protected by a continuous hoops of bone. It is quite possible that this construction was necessary for protection, not against prey, but against the risk of falling, as discussed on a previous page. These springy bone hoops might have done much to absorb the shock of impact. Lambe also speculates that this elastic system might have served some respiratory function, which sounds reasonable, if speculative. In any event, he notes that the ribs were constructed so as to lock together when pushed, pulled or impacted, which would have served a shock-absorbing function all the better. [5] This is not at all clear -- either from the figures or the measurements of the bones given by Lambe. [6] Lambe notes that the curvature of the femoral head splayed the femur out, while compensating asymmetry of its distal condyles would have directed the shank medially. The net result was that Gorgosaurus was "bow-legged" but would have walked erect, not sprawled.

Images: all images from [L17].

Links: DinoData Dinosaurs G043 GORGOSAURUS; Gorgosaurus Fact Sheet - EnchantedLearning.com; GORGOSAURUS; Gorgosaurus Dutch); gorgosaurus; Gorgosaurus; Webshots Community - Gorgosaurus libratus;  All Gorgosaurus Gus Photos Photos; Media Information; Gorgosaurus libratus; Photographer Darren Tanke; Albertosaur Systematics.     

References: Carpenter & Smith (2001) [CS01]; Holtz (2001a) [H01a], Lambe (1917) [L17]. ATW021216.

Tyrannosaurini: Definition: Tyrannosaurus > (Albertosaurus or Gorgosaurus). Includes: Daspletosaurus, Dinotyrannus?, Tarbosaurus, Tyrannosaurus.

Range: Late Cretaceous (Late Campanian to Maastrichtian) of North America and East Asia.

Phylogeny: Tyrannosaurinae: (Albertosaurus + Gorgosaurus) + *.

Characters: lacrimal horn absent; widely expanded occiput relative to snout width resulting in orbits having a forward-pointing component; ventrally deflected occipital condyle; intramandibular joint frozen by (a) supradentary overgrowing joint and fusing with coronoid (b) long process of prearticular articulating with both coronoid & splenial, (c) angular anterior process bridges gap ventrally; and (d) supradentary sends ridges between the teeth [HC00].

Links: Re- Dwarf Tyrannosaurs; Re- Tyrannosauridae; What's the difference between Tyrannosauridae, Tyrannosaurinae, ...; Nanotyrannus; Gigadispute..

References: Hurum & Currie (2000) [HC00]. ATW030425.

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