Tyrannosauroidea

    I'll admit it.  I'm guilty of not being as impressed as a lot of other people are with tyrannosaurids and their kin, who count among their members an animal I would consider at least the second most popular of classic dinosaurs, Tyrannosaurus rex.  They're all right as far as theropods go, but I lean more towards megalosaurids, allosaurids, and smaller coelurosaurians.
    Tyrannosaurids are easily recognized by their two-clawed hands carried at the end of very short arms, big ol' skulls with a fair degree of binocular vision, running hindlimbs, and robust teeth.  A peculiar feature of tyrannosaurids is that the teeth in the premaxillae, at the front end of the upper jaw, have D-shaped cross sections.  So far, all tyrannosaurids come from the LK of Asia and North America; teeth are known from the EK of Japan, and tyrannosaurid remains also are known from the Mussentuchit Member of the Cedar Mountain Formation.  For more information on tyrannosaurids and their allies, please see The Tree of Life's tyrannosaur pages. 

<--Tyrannosauroidea
     |--?Bagaraatan
     `--+--Guanlong
          |--Stokesosaurus
          `--+--Dilong
               |--Dryptosaurus
               |--Eotyrannus
               `--+--Appalachiosaurus
                    `--Tyrannosauridae
                         |--Albertosaurinae
                         |    |--Albertosaurus
                         |    `--Gorgosaurus
                         `--Tyrannosaurinae
                              |--Daspletosaurus
                              `--+--Tarbosaurus
                                   `--Tyrannosaurus            
           
Tyrannosauroidea: Very basal tyrannosauroids had three fingers per hand, were in the 3-4 m long range, and in general looked a lot like other basal coelurosaurians.

Taxon or Taxa: Time\Place: Comments:
?Bagaraatan ostromi Osmolska, 1996 early Maastrichtian (LK) of Mongolia This basal coelurosaurian\tyrannosauroid is based on a partial lower jaw, some of the vertebrae, and hindlimb material.  Its type remains were discovered in 1970, but went undescribed until recently.  The lower jaw looks powerful.
Remains from what may be a related theropod are known from the Hateg Basin of Romania, with a similar age.
Guanlong wucaii Xu, Clark, Forster, Norell, Erickson, Eberth, Jia, and Zhao Q., 2006  Oxfordian (LJ) of China Known from two mostly complete and articulated skeletons, Guanlong is most remarkable for its cranial crest, a thin pneumatic midline structure that in gross morphology looks something like the crests of Dilophosaurus.  Like other basal tyrannosauroids known from good material, it looked not unlike Ornitholestes or Tanycolagreus, a ~3 m long biped with long arms and a stout rectangular skull (not counting the crest).  The hole for the snout is relatively large.  Despite its overall basal coelurosaurian look, the pelvis and the lower jaw definitely have that tyrannosaur look (even if you don't like tyrannosaurs all that much, if you look at enough illustrations of dinosaur bones, some things will just stand out over time).
One individual, the type, appears to have been a mature 12-year-old at death, while the other may have been 6.
Obviously, the early LJ age is drawing a lot of attention, but given how comparable something like this is to known basal coelurosaurians from the Morrison, it shouldn't be entirely unexpected. 
Stokesosaurus clevelandi Madsen, 1974 late Kimmeridgian (LJ) of Utah and South Dakota Like Iliosuchus, this taxon is based on an ilium with a distinctive vertical ridge (and has been informally considered an "iliosuchid" at times in the past, including by me).  A premaxilla and braincase are suggested to belong as well.  This braincase is advanced and tyrannosaurid-like.
Dilong paradoxus Xu, Norell, Kuang, Wang, Zhao Q., and Jia, 2004 Valanginian-early Barremian (EK) of China This new basal tyrannosauroid, from the lower Yixian, had protofeathers (so far found preserved around the tail and the rear of the lower jaw).  It is based on three specimens, with a possible fourth that could turn out to be a new species of the same genus, including excellent skulls and most of the postcrania, showing it to have had three fingers per hand, a long compsognathid-like pubic boot, and a gracile build.  The largest specimen was estimated at 1.6 m long.  All in all, it had a sort of Ornitholestes-Compsognathus look to it.  The name means "emperor dragon", with paradoxus referring to the unusual skeletal features.
Dryptosaurus aquilunguis Marsh, 1877 (originally Laelaps aquilunguis Cope, 1866) late Campanian-early Maastrichtian (LK) of New Jersey One of the first North American dinosaurs known from good remains, Dryptosaurus is well known as the subject of the late 19th century "fighting dinosaurs" painting, where one Dryptosaurus is leaping upon another.  It also has an unusually large hand claw.  Classification-wise, it has bounced around a great deal, in the past usually stuck with the "megalosaurids" or tyrannosaurids, and it seems to be turning out to be a basal tyrannosauroid.
Eotyrannus lengi Hutt, Naish, Martill, Barker, and Newberry, 2001 Barremian (EK) of England Newly described, this Wealden animal is apparently a basal tyrannosauroid.  It is known from part of the skull and limbs of a partially grown individual.  Interestingly, it had longish arms.  Exaggerated reports of a "cat-like" theropod were based on this animal.
Appalachiosaurus montgomeriensis Carr, Williamson, and Schwimmer, 2005 middle Campanian (LK) of Alabama Alabama's second named dinosaur (the other being Lophorhothon), Appalachiosaurus had been floating around in conversation as Albertosaurus sp. for more than fifteen years.  It is based on the partial skeleton of a partially-grown individual, including a partial skull (the biting portion, mostly), much hindlimb material, parts of the lower pelvic bones, and a few caudals (including two that are fused).  The known remains are not vastly unlike Albertosaurus or Gorgosaurus, especially a young, gracile individual, and another analysis finds it to be an albertosaurine.  This find also extends our information on East Coast Late Cretaceous (well, anytime, really, since the East Coast is pretty barren after the early Jurassic) dinosaurs.

Tyrannosauroidea i.s.:

Taxon or Taxa: Time\Place: Comments:
Aviatyrannis jurassica Rauhut, 2003 Kimmeridgian (LJ) of Portugal Based on a small ilium (9 cm long) reminiscent of Stokesaurus, Aviatyrannis is considered a very basal tyrannosauroid.  In fact, the remains first referred to Stokesosaurus from Portugal comprise the holotype.  It has been suggested that some material from the Morrison may pertain to it.
?Labocania anomala Molnar, 1974 Campanian (LK) of Mexico This is a large, unusual, poorly preserved theropod, known mostly from fragmentary cranial remains, along with a partial ischium and metatarsal.  Some of its material has features like those of abelisaurids, some is like those of allosaurids, and some is like those of tyrannosauroids.
"Tonouchisaurus mongoliensis" (N.N.) Barsbold, 1994 EK of Mongolia This is apparently a small, basal tyrannosauroid, with two fingers per hand.  It is based on a headless skeleton.

Tyrannosauridae i.s.:  Each of the Big 5 genera has at one time or another been considered a synonym of just about everyone else here.  There is a strong lumper and splitter view on the species herein.  From the extreme lumpers, you might see two genera: Tyrannosaurus and Albertosaurus.  From the moderate lumpers, you keep most of the taxa but lose the mini-tyrannosaurines as juveniles of others.  From the hard-line splitters you get an amazing proliferation of tyrannosaurid taxa.  I am a moderate lumper when it comes to Tyrannosaurus, but a moderate splitter when it comes to the albertosaurines.  The two divisions of albertosaurine and tyrannosaurine appear good; albertosaurines are more gracile, smaller, and have distinctive preorbital prominences, while tyrannosaurines are larger, more robust, and have distinctive postorbital horns.  However, all tyrannosaurids are very similar in general appearance.
   New research indicates that tyrannosaurids had a very fast rate of growth.  Most tyrannosaur bones undergo considerable change and remodeling during growth, but the fibula does not, and will provide growth lines.  From this information, it appears that tyrannosaurids grew slowly until they were around 12 years old, then went through a stupendous growth spurt until about age 18, and then stopped growing, dying before 30.  In the case of Tyrannosaurus rex, the growth spurt would have necessitated putting on about 5 pounds a day during the period of greatest growth.  Tyrannosaurids varied in the amplification of the growth spurt, the earlier smaller taxa like Albertosaurus and Gorgosaurus having a smaller maximum growth rate than their later, bigger relatives (Erickson, Makovicky, Currie, Norell, Yerby, and Brochu. 2004. Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs. Nature 430, 772-775.).  
   Tyrannosaurids used to be divided into two general groups: aublysodontines and tyrannosaurines.  Aublysodontines were supposedly much smaller, between dromaeosaurids and tyrannosaurines in size, and were much less well known.  They were based on distinctive unserrated premaxillary teeth, which have since turned out to be the teeth of young tyrannosaurids for the most part.

Taxon or Taxa: Time\Place: Comments:
"Albertosaurus" periculosus (N.D.) Riabinin, 1930 ?early Maastrichtian (LK) of China This is an indeterminate tyrannosaurid based on a tooth.
Alectrosaurus olseni Gilmore, 1933 early Maastrichtian (LK) of China Alectrosaurus is based on material that originally included a big, robust humerus.  This bone now appears to have belonged to a therizinosaurid, while the rest of the material pertains to this taxon, a basal tyrannosaurid of uncertain affinities.  Remains from several individuals are known, including a partial skull.
Alioramus remotus Kurzanov, 1976 early Maastrichtian (LK) of Mongolia This tyrannosaurid is distinguished by its gracile lower jaw and the unusual small horns running down the midline of its skull.  This type skull is possibly a juvenile.
Aublysodon mirandus (N.D.) Leidy, 1868  Campanian-Maastrichtian (LK) of Alberta, Montana, Colorado, Wyoming, and New Mexico This animal is based on premaxillary teeth from a young tyrannosaurid of uncertain taxonomy.  Similar teeth are commonly found in the LK of North America.
"Aublysodon":  "A." amplus (N.D.) Marsh, 1892 late Maastrichtian (LK) of Wyoming These are a couple of tooth taxa based on juvenile tyrannosaurid teeth.
"A." cristatus (N.D.) Marsh, 1892
?"A." lateralis (N.D.) Cope, 1876 late middle Campanian (LK) of Montana This is a tooth taxon that may or may not belong here.
Deinodon horridus (N.D.) Leidy, 1856 late middle Campanian (LK) of Montana This tooth taxon from the early days of dinosaur paleo is probably synonymous with Gorgosaurus, but there is not enough evidence to be certain of this.  Incidentally, Tyrannosauridae was once called Deinodontidae (and technically should still be, really).
?"Futabasaurus" (N.N.) Lambert, 1990 Coniacian-Santonian (LK) of Japan This taxon is apparently a tyrannosaurid of some sort.  The name has now been published for an elasmosaurid plesiosaurian (one of those plesiosaurs with the super-long necks), so it'll be interesting to see if these are two separate animals, or a reinterpretation of a tyrannosaurid into an elasmosaurid.
"Ornithomimus" grandis (N.D.) Marsh, 1890 early Campanian (LK) of Montana Based on a foot, this species is an indeterminate tyrannosaurid sometimes referred to Albertosaurus.
"Tyrannosaurus" zhuchengensis (N.D.) Hu, Cheng, Pang, and Fang, 2002  early-mid Maastrichtian (LK) of China Based on a metatarsal and three teeth, this species is probably best considered an indeterminate tyrannosaurid at this point.

Albertosaurinae:  Formerly, the three members of this group were considered synonymous.  In the 1970s Daspletosaurus was separated.  Now, because of the ambiguity of the type of Albertosaurus, Gorgosaurus has once again been separated.  It is now considered a fairly safe practice to refer only gracile late Campanian albertosaurine remains from certain formations in Alberta to Gorgosaurus, robust remains from the same time and places to Daspletosaurus, and early Maastrichtian Alberta remains to Albertosaurus, while considering all albertosaurine remains not from these times and places to be Albertosaurinae i.s., until further notice.  However, all three of them could easily belong to the same genus, Albertosaurus, though as different species. 

Taxon or Taxa: Time\Place: Comments:
Albertosaurus sarcophagus Osborn, 1905 early Maastrichtian (LK) of Alberta Stripped of the remains assigned to Gorgosaurus, this taxon is known mainly from two partial skulls and skeletons, although bonebed material has been recently found that could add 9 individuals in three general size classes.
Gorgosaurus libratus Lambe, 1914 (?Albertosaurus) late middle Campanian (LK) of Alberta This is the animal commonly illustrated as Albertosaurus.  It is known from more and better material than its close relative, including several described partial skulls and skeletons and additional bonebed material.  It is a characteristic Judithian theropod, and was more common than its relative and contemporary Daspletosaurus.  Juvenile material is known as well, showing gracile animals with very large teeth relative to skull size (although some of these juveniles may belong to Daspletosaurus).

Tyrannosaurinae:  As explained before, the tyrannosaurines are a tangle.  Some people would have all of these taxa comprised in a single genus, while others propose at least six or seven genera.  They are all very similar animals.  Tyrannosaurines lack the preorbital horns of albertosaurines, instead having large postorbital bosses. 

Taxon or Taxa: Time\Place: Comments:
Daspletosaurus torosus Russell, 1970 (?Albertosaurus or Gorgosaurus) late middle Campanian (LK) of Alberta Sometimes confused with its relative Gorgosaurus, this theropod may be close to the ancestry of Tyrannosaurus.  It is easily the least famous of the big North American tyrannosaurids.  A unique feature of this taxon is the length of the arms; it has the longest arms, relative to size, of any of the derived tyrannosaurids.
New material indicates that a previously unknown species existed in the late Campanian (LK) of New Mexico, a member of a distinct southern U.S. fauna including dinosaurs like Pentaceratops, Kritosaurus, and species of Parasaurolophus.
Tyrannosaurus: Osborn, 1905  T. rex (type) Osborn, 1905 (including Stygivenator molnari Olshevsky, 1995 [originally Aublysodon molnari Paul, 1988]) late Maastrichtian (LK) of Alberta, Saskatchewan, Colorado, Montana, Wyoming, N./S. Dakota, Utah, ?New Mexico, and ?Texas This is the famous T. rex every schoolchild knows about.  It is one of the largest theropods, probably the fastest for its size, and had a set of wickedly powerful jaws with thick teeth.  Just recently a bread-loaf sized piece of fossilized dung (coprolite) that was very likely produced by a member of this species was found, and it proved to have chopped-up prey bones contained within.  It is a signature Lancian dinosaur.  
The story of Nanotyrannus lancensis, here considered a juvenile of its own species within Tyrannosaurus, is long and unusual.  Based on an excellent skull that sat for decades in a museum's storage under the name of Gorgosaurus lancensis, this specimen was rediscovered in the late 1980s, and immediately became a favorite for scanning with various high-tech devices.  Although at first considered to be a separate taxon, due to what looked like strong, adult-type fusion of the skull bones, studies of young tyrannosaurids indicate it probably is not.  However, it has more teeth than adult T. rex, which could be good enough for a specific differentiation.  
Similarly, the snout, incorrectly restored with an upturned tip and once named Stygivenator most likely belongs to a young T. rex as well; the so-called "Jordan theropod," it bounced around from dromaeosaurid to tyrannosaurid to a species of Aublysodon.  A partial skeleton and skull from New Mexico thought to belong to it may actually pertain to an albertosaurine.
The famous "Sue" is, alas for romanticism, most likely not as beat-up in life as it was thought, and is as likely to be male as female (the evidence of chevron location and build overturned when an additional chevron was found to go between two caudal verts at the base of the tail where it was suggested that females lacked a chevron for ease of egg-laying).
The hunting strategy for this beast is now suggested as neck-crushing; the large powerful jaws make ideal implements for delivering heavy bites to hadrosaurid necks.  In addition, the short but strong forelimbs (with two "finger" fingers and a reduced III, much like other tyrannosaurids) appear to be best suited for tightly clutching struggling prey while the jaws do their work.
T. lancensis (Bakker, Currie, and Williams, 1988 [originally Gorgosaurus lancensis Gilmore, 1946]) late Maastrichtian (LK) of Montana
Tarbosaurus bataar (Maleev, 1955 [originally Tyrannosaurus])  (including Maleevosaurus novojilovi Carpenter, 1992 [originally Gorgosaurus novojilovi Maleev, 1955], and Shanshanosaurus huoyanshanensis Dong, 1977) early Maastrichtian (LK) of Mongolia and China This taxon is very close in anatomy to its American cousin, and may be congeneric.  It was probably a hunter of the numerous hadrosaurids with which it shared its environment.  
Included within Tarbosaurus is Maleevosaurus novojilovi, one of the "mini-tyrannosaurs".  Like Nanotyrannus, it is apparently a juvenile.  Very large specimens of Tarbosaurus, in the range of T. rex, are known, but rare; it was on the whole smaller than its North American cousin.
Based on a partial skull and postcranium from a juvenile individual, Shanshanosaurus was regarded as a mysterious animal, something like a cross between a dromaeosaurid and a tyrannosaurid.  Further research suggests that it was a juvenile Tarbosaurus.

 

Navigation
Home Page Alphabetical Dinosaur Index Clado-Index
Background Information Glossary Faunae