Abelisauridae

    Abelisauridae is a clade of theropods that was first described in the mid 1980s, from Abelisaurus and Carnotaurus, two new LK species from Argentina.  So far, they are known mostly from the late Cretaceous of the Southern Hemisphere.  Many of them appear to have been fairly large.  They were the Gondwanan equivalent of the tyrannosaurids, being the top predators (after the spinosauroids and carcharodontosaurids were out of the way in the early Late Cretaceous).  However, they probably went about their business in different ways than tyrannosaurids, given their less cursorial builds (abelisaurids seem to have been longer and lower than tyrannosaurids, from what we currently know), less robust skulls and teeth, and different prey items (Gondwanan continents being overrun with titanosaurians and with not much in the way of hadrosaurids, ankylosaurians, or ceratopians).
    So far, there are carnotaurine abelisaurids and a few non-carnotaurines.  Carnotaurines are known for very short arms practically lacking the forearm segment, and for elaborate horns and knobs on the skull.  Abelisaurid skulls are known for having deep upper jaws with tall snouts, and slim lower jaws.  They also have "cheeks" expanded side to side, like those of tyrannosaurids, perhaps conferring an additional degree of binocular vision over predators with more narrow skulls. 
    Besides its two founding members, Abelisaurus and Carnotaurus, Abelisauridae has become a home for a number of poorly-known theropods whose affinities had previously been unknown.  With the recent flood of good material from South America and Madagascar, it is very likely that this group will continue to increase in size.   

<--Abelisauridae
      |--Rugops 
      `--+--Abelisaurus
            `--Carnotaurinae
                 |--Ekrixinatosaurus
                 |--Majungasaurus
                 |--Rajasaurus
                 `--+--Aucasaurus
                       `--Carnotaurus
                 
Abelisauridae:

Taxon or Taxa: Time\Place: Comments:
Rugops primus Sereno, Wilson, and Conrad, 2004 Cenomanian (LK) of Niger Rugops is a new hornless (no bony horns, at least) basal abelisaurid, known from a partial skull lacking the palate and most of the bones along the side of the face behind the eyes.  This skull is distinguished by a row of depressions along the upper surfaces of the nasals, and by a small hole between the lacrimal, prefrontal, frontal, and postorbital (which is a little sketchy on absolute dimensions given that the postorbitals are AWOL).  It has been suggested that these holes held blood vessels to supply a nonbony keratinous or fleshy ridge or crest system.  I like the name; it is short and direct, like a good predator ought to be.
Abelisaurus comahuensis Bonaparte and Novas, 1985 Santonian-early Campanian (LK) of Argentina Known only from a nearly complete skull, Abelisaurus is usually regarded as closely related to Carnotaurus, although that may seem hard to believe based on the superficial aspects of the skulls (and some researchers have recently suggested that it may be a late-surviving carcharodontosaurid).  It is one of my favorite big theropods; I like the no-nonsense look of the skull.

Abelisauridae i.s.: There are a number of poorly-known abelisaurids described from India (Huene and Matley had a great big monograph back in 1933) that have suffered greatly, first from initial misinterpretations (and the fact that they weren't complete enough to draw good comparisons), and later from specimen loss; a great deal of the convoluted taxonomy could probably be cleaned up if the original specimens could be located.  For example, it is entirely within the realm of possibility that Indosaurus, Indosuchus, and Compsosuchus are the same thing, and Lametasaurus and Rajasaurus the same thing.  It appears that there were at least two large theropods, possibly three, in the Lameta, one represented by Indosuchus, one represented by Carnotaurus-like Rajasaurus, and a possible non-abelisaurid abelisauroid (suggested by some skull elements with non-abelisaurid features).
    An abelisaurid tooth, previously referred to Majungasaurus, is known from the Maastrichtian (LK) of Egypt.

Taxon or Taxa: Time\Place: Comments:
Compsosuchus solus (N.D.) Huene and Matley, 1933 (?Indosuchus or ?Rajasaurus) Maastrichtian (LK) of India Interestingly, the axis cervical that forms the type of this species (and is AWOL), while on the whole corresponding well with carnotaurine axial verts, has some similar characteristics to that of the carnosaurian tetanuran Allosaurus.  Thus, this theropod shows some convergence with Allosauridae.  It used to be considered a "coelurid" or compsognathid.
Dryptosauroides grandis (N.D.) Huene and Matley, 1933 Maastrichtian (LK) of India This theropod is based upon six incomplete caudals that have no features that would allow it to be distinguished from the multitude of other dubious theropods from the Lameta Formation, or from Majungasaurus.  It would have been large, though, on the order of Carnotaurus in size.
Indosaurus matleyi Huene and Matley, 1933 (?Indosuchus) Maastrichtian (LK) of India I am sad to report that Indosaurus does not appear to have had horns after all, and could potentially be the same as Indosuchus (unfortunately the type material is lost).  It was once identified as an allosaurid or "megalosaurid".
Indosuchus raptorius Huene, 1932 (?Compsosuchus, ?Indosaurus) Maastrichtian (LK) of India This theropod is based on currently absent skull material.  It was a contemporary of Rajasaurus and (possibly synonymous) Indosaurus, but appears to be closest to Abelisaurus and Majungasaurus.  It was originally identified as a tyrannosaurid.
Much new material has been assigned to it, making up most of a skeleton. This material includes a relatively long arm, especially when compared to Carnotaurus.  Unfortunately, the fact that several other large theropods (possibly synonymous) are known from the same time and place means that this identification is not secure. 
Ornithomimoides: (N.D.) Huene and Matley, 1933 O. mobilis (N.D.) (type) Huene and Matley, 1933 Maastrichtian (LK) of India The caudals assigned to these two species are inadequate for classification beyond Abelisauridae, and are essentially identical to those of MajungasaurusO mobilis was based on five caudals (thought to be dorsals), and O. barasimlensis was based on four smaller caudals (again, thought to be dorsals).
O. barasimlensis (N.D.) Huene and Matley, 1933

Carnotaurinae:  This is a sort of theropodian "rogue's gallery," where the members are outlandish in appearance.  Horns above the eyes (Carnotaurus means "meat-eating bull"), extraordinarily deep skulls matched with slender dentaries, tiny, seemingly useless arms and hands, and strange thickening of the skull roof are things seen in some or all of these creatures.  It is most probable that the cranial ornamentation was used for display.  Carnotaurines also have L-shaped "wings" (sticking out and up on the long end of the L, with the short end pointing forward) for transverse processes on the caudal verts.
    Carnotaurines, particularly the distinctive namesake, have become the go-to theropods when someone wants to depict a theropod that is not either Tyrannosaurus, Velociraptor (or another "raptor"), or Allosaurus.    

Taxon or Taxa: Time\Place: Comments:
Ekrixinatosaurus novasi Calvo, Rubilar-Rogers, and Moreno, 2004 Cenomanian-early Turonian (LK) of Argentina Ekrixinatosaurus (name means "explosion-born lizard," referring to being discovered during a blasting operation) is based on a fair amount of a skeleton belonging to a single individual, about 6 m long from its skeletal restoration.  Both maxillae and dentaries, part of the braincase, a couple of cervicals, many dorsals, the sacrum, anterior-middle caudals, most of the pelvis (except for the distal ischia), ribs, most of one hindlimb, and the knee of the other hindlimb were preserved.  It has standard "carnotaur" caudal process wings and pelvic form.  
It has a relatively bigger head than Carnotaurus (extrapolated skull-femur ratio 1.00 compared to 0.58), but is not particularly unique compared to other abelisaurids (some different proportions and holes and depressions on the verts, and so on).
Majungasaurus crenatissimus Lavocat, 1955 (originally Megalosaurus crenatissimus Depéret, 1896; including Majungatholus atopus Sues and Taquet, 1979) mid Maastrichtian (LK) of Madagascar This theropod has been through a mess.  For a long time, there was Megalosaurus crenatissimus, or Dryptosaurus crenatissimus, or Majungasaurus crenatissimus, a large theropod.  Then, there was Majungatholus, thought to be a large, strange pachycephalosaurid.  Then, a recently-discovered skull set the record straight partially by showing that Majungatholus was really a theropod.  Because the crenatissimus material wasn't the greatest, it was left out of the party until there were enough remains to show that indeed it was the same as Majungatholus and by priority should be the name used.
In one of those things that happen, "Megalosaurus" crenatissimus and Majungasaurus actually are based on different material.  Depéret based his species on a collection of teeth, verts, and a phalanx, with no actual holotype, whereas Lavocat designated a Carnotaurus-like dentary from an immature individual as the neotype for Majungasaurus, while explicitly recognizing "M." crenatissimus and Majungasaurus to be the same thing.
Among the many interesting skull features are the thickened nasals, a horn on the frontal, a parietal prominence, and pneumatic chambers.  Remains from several individuals and size classes are known.  Tooth markings on some remains suggest cannibalism.
Rajasaurus narmadensis  Wilson, Sereno, Srivastava, Bhatt, Khosla, and Sahni, 2003 Maastrichtian (LK) of India Based on material including a skull with a low horn, hip material, caudals, and hindlimb material, this new large abelisaurid puts interesting questions to those who delight in taxonomy, given the tangled state of theropod taxonomy of the Lameta Formation of India.  It may put to rest some of the controversy surrounding Lametasaurus, as its ilia are very similar to the ilia included in the material of the latter.
Aucasaurus garridoi Coria, Chiappe, and Dingus, 2002 Santonian (LK) of Argentina This carnotaurine is based on an almost complete skeleton back to the 13th caudal, including soft tissue impressions about the hips.  The animal is considered to be about 70% of Carnotaurus' size, with a longer, lower skull with bumps instead of horns, but very similar to the other animal.  The arms were also somewhat longer.  
It had been buried in a shallow lake; damage to the skull suggests it had been involved in a fight shortly before death.
Carnotaurus sastrei Bonaparte, 1985 Maastrichtian (LK) of Argentina This theropod is known from some of the best material of any dinosaur.  Its type is a virtually complete skeleton and skull with extensive skin impressions, showing this animal to have had widely-spaced rows of small scutes, in addition to the bony horns which give this theropod its name.  Its hands and arms were so small as to be virtually useless; for example, the lower arm bones (ulna and radius) were functionally part of the hand.  Once dated to the "middle" Cretaceous, it is now known to be much younger.

Carnotaurinae i.s.:

Taxon: Time\Place: Comments:
?Quilmesaurus curriei Coria, 2001 mid Campanian (LK) of Argentina Based on a small to medium sized femur and tibia, Quilmesaurus initially defied classification, but it now appears as though this animal probably was a carnotaurine.

 

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