Coelurosauria
The second great division of Avetheropoda, Coelurosauria is beyond
any doubt the most diverse group of theropods, even without factoring in birds.
There are giant superpredators (tyrannosaurids),
toothless racers (ornithomimids), two kinds of
sickle-clawed birdlike hunters (dromaeosaurids and troodontids), strange sloth-like herbivores with giant hand
claws (therizinosaurians), little animals with an
unknown diet and bizarre mandibles and sometimes head crests (oviraptorids and caenagnathids, on the same page), and
some of the smallest known classic theropods (compsognathids).
They all tend
to have relatively long arms, except for the tyrannosauroids which secondarily shortened
them, probably for weight reduction, and the alvarezsaurids,
who may have been actual birds but reduced their arms to powerful single-clawed stubs,
possibly for digging. All members of
Coelurosauria may have been feathered or derived from ancestors who had that
characteristic.
Tyrannoraptora has been named for the combination of
Tyrannosauroidea and Maniraptoriformes, which corresponds in membership to my
old Maniraptoriformes, back when I had Arctometatarsalia. An important
historical development in Tyrannoraptora is the Tyrannosauroidea\Arctometatarsalia
saga, wherein Tyrannosauroidea was introduced to Coelurosauria as a member of a larger
grouping known as Arctometatarsalia, which also was to include ornithomimosaurians,
elmisaurids,
and troodontids. The key character linking these
diverse groups was the third metatarsal's relationship with the second and fourth
mets. In arctomets, the third metatarsal was pinched off at the top in front
view. Later, it became clear that most groups of "arctomets" had acquired this
condition convergently; this category includes the elmisaurids, which are closely related
to the oviraptorids, the ornithomimosaurians, and the troodontids, which had
been classified in a group with the ornithomimosaurians because they shared similar
swellings in a bone of the braincase (Bullatosauria, or "inflated lizards"), but
now appear to be closer to the dromaeosaurids. Tyrannosauroidea and Ornithomimosauria,
or Ornithomimosauria and Alvarezsauridae, are
about the only groups that people will occasionally still link as arctomets, but
even these small versions of Arctometatarsalia are going by the wayside, as it becomes more
and more evident that the arctomet was just a good anatomical idea that several
different groups found at different times, or an idea present at the base of,
say, Tyrannoraptora, that was further expanded upon or lost by the more derived
groups (this second option seems better as we get more information on the basal
members of those groups, something we didn't have before).
<--Coelurosauria
|--Compsognathidae
| |--Huaxiagnathus
| `--+--?Sinosauropteryx
|
`--+--Mirischia
|
`--Compsognathus
`--+--Nedcolbertia
|--?Scipionyx
`--+--"Ornitholestidae"
| |--Nqwebasaurus
| |--Ornitholestes
| `--Proceratosaurus
`--Tyrannoraptora
|-->Tyrannosauroidea
`--+--Coelurus
`--Maniraptoriformes
|-->Ornithomimosauria
`-->Maniraptora
Maniraptoriformes incertae sedis:
Alvarezsauridae
|--Alvarezsaurus
|--Patagonykus
`--Mononykinae
|--Mononykus
|--Shuvuuia
`--Parvicursor
Compsognathidae: Compsognathids are renowned as the smallest known adult classic
dinosaurs, measuring somewhat over a meter in length fully grown in some cases (although their
lofty status appears to be in doubt; see Microraptor). Compsognathids were small, fleet theropods with very long tails and
reduced arms. Indeed, until the discovery of Sinosauropteryx's three clawed
hands it was believed compsognathids had only two fingers per hand, a result of the
ambiguous condition of the hands in Compsognathus specimens. These animals
were small game hunters, as shown by the discovery of mammal and lizard remains in the
belly region of several specimens.
Compsognathidae may be an artificial assemblage of a variety
of small basal coelurosaurs, some of which may pertain to a true Compsognathidae,
others to basal Tyrannosauroidea (it turns out that basal tyrannosauroids were
not all that different from generalized basal coelurosaurs).
Material from the EK of Thailand may be referable to this family.
| Taxon or Taxa: | Time\Place: | Comments: |
| Huaxiagnathus orientalis Kwang, Norell, Qiang, and Keqin, 2004 | mid Barremian-early Aptian (EK) of China | Based on two skeletons, including one very good nearly complete specimen, Huaxiagnathus (known as "Huaxiasaurus" in early reports), is a big compsognathid (well, big for a compy, with the subadult type at maybe 1.6 m long). The skull is also very large and robust for a compy, with a deep maxilla giving a very rectangular skull in side view. There are unusual blobs in the rib cage of the type specimen which could have been something it ate. Because of the preservation, no integument has been found, fuzzy or not. |
| ?Sinosauropteryx prima Ji Q. and Ji S., 1996 | mid Barremian-early Aptian (EK) of China | This taxon, known from three virtually complete specimens
including possible stomach contents (lizards and mammals), unlaid eggs, and "protofeathers," is similar
in many ways to Compsognathus. Although most scientists
accept that the fibers seen on Sinosauropteryx have at least
something to do with feathers or "protofeathers," others claim
they are actually part of a soft ridge, like those seen on marine
iguanas. There is evidence that appears to negate this, though (for
example, the fibers seem to cross each other often, and are found in
places where a ridge would not be present unless compsognathid anatomy is
quite a bit wilder than expected). Some of the
objects feature dark stripes, which could be remnants of original
pigmentation patterns; this would suggest a banded tail. Of the original three specimens referred to this taxon, two (including the holotype) might not be compsognathids, instead being more like basal carnosaurians, while the third might be a compy. They had long tails, short arms, and big first digits on the hands. |
| Mirischia asymmetrica Naish, Martill, and Frey, 2004 | ?Albian (EK) of Brazil | Well-known for several years as the undescribed Santana Formation compsognathid, or as its specimen number SMNK 2349 PAL, Mirischia's remains include a possible preserved air-sac and chunk of intestine, along with a pelvis, hindlimb material, and dorsal and sacral verts. Its species name comes from the fact that the two hips differ in prominent details that have often been considered taxonomically significant, but now, maybe not so much. |
| Compsognathus longipes Wagner, 1859 | ?Tithonian (LJ) of Germany and France | Compsognathus is known from most of two skeletons, one from Germany and a second, larger one from France (incidentally, this French Compsognathus was originally described as a different species, C. corallestris Bidar, Demay, and Thomel, 1972, that was believed to have had flippers, but this was shown to be incorrect). The type, a partially-grown individual, has the remains of a lizard in its belly region; other odd structures in the body could be eggs. The French specimen has disarticulated small reptile remains in its gut region as well. It has a long pubic boot with little forward expansion, similar to that of Coelurus, which is often missed in restorations (which are also typically done from the juvenile specimen). |
Compsognathidae i.s.:
| Taxon or Taxa: | Time\Place: | Comments: |
| Aristosuchus pusillus Seeley, 1887 (originally Poikilopleuron [Owen, 1876]) | Barremian (EK) of England | Often confused with Calamospondylus, Aristosuchus appears to be a valid compsognathid based on the structure of its pubis; other remains may be referable. At a possible length of 2 m, it would have been a rather large compsognathid. |
| ?Juravenator starki Göhlich and Chiappe, 2006 | latest Kimmeridgian (LJ) of Germany | After several years as the skull and
cervicals known as "Borsti," this compsognathid now sees the
light of day, and as a nearly complete skeleton, no less (the specimen was
in a block of limestone and CAT scanning revealed the rest of the
body). Only the last third of the tail is missing. The
individual appears to have been a juvenile. Unlike Sinosauropteryx, this animal had at least a featherless mid-tail with typically dinosaurian small pebbly scales. It was found in what can only be described as an endearing death pose (except for one wonky leg): arms tucked in shyly, head turned so it appears to be looking over the shoulder, and an aesthetically-pleasing curve to the tail. Some researchers have called the cladistic analysis in the description into question, but when all is said and done, this animal will probably still end up as a compy-like basal coelurosaurian of some stripe. |
| Sinocalliopteryx gigas Ji S., Ji Q., Lü J., and Yuan C., 2007 | mid Barremian-early Aptian (EK) of China | Sinocalliopteryx was a large compsognathid (the largest known at the time of description), larger than Huaxiagnathus but rather similar. It is based on a complete skeleton, with filament-style integument and a dromaeosaurid leg in its abdomen (eaten, not left there by an amputee dromaeosaur). |
Other Coelurosauria: A new basal coelurosaurian, based on two partial skeletons from the middle Turonian (LK) of New Mexico, is currently being described. Also, a possible basal coelurosaurian femur is known from the EK Wealden Formation, and a 7-8 meter long form has been uncovered in the LK of Argentina, with partial skeleton and skull. Basal coelurosaurians in general are a bit of a mess.
| Taxon or Taxa: | Time\Place: | Comments: |
| Nedcolbertia justinhofmanni Kirkland, Britt, Whittle, Madsen, and Burge, 1998 | early Aptian (EK) of Utah | A recently-described taxon known from three partial skeletons, Nedcolbertia is similar in many ways to Ornitholestes, but also is like the compsognathids. |
| ?Scipionyx samniticus Sasso and Signore, 1998 | Aptian (EK) of Italy | "Skippy," as it is known informally, is based on the small partial skeleton of a juvenile (?hatchling) coelurosaurian (possibly more derived, but characters uncertain due to youth and missing areas) that preserves traces of intestines, the trachea, muscle fibers, and other organs, the first ever classic dinosaur to have its remains show such soft parts. It is also the first named classic dinosaur from Italy. It could be a compsognathid. |
Coelurosauria i.s.:
| Taxon or Taxa: | Time\Place: | Comments: | |
| ?"Allosaurus" medius (N.D.) Marsh, 1888 | late Aptian-early Albian (EK) of Maryland | "A." medius is based on a tooth showing similarities to Dryptosaurus. | |
| Aniksosaurus darwini Martinez and Novas, 2006 | Cenomanian-Turonian (LK) of Argentina | Aniksosaurus was a small but robust basal
coelurosaurian of uncertain affiliation. It is known from the
remains of at least five individuals found in a single small bonebed, with
no other animals. Five right tibiae at the discovery locality give
us the minimum number of individuals; either five were present, or this
animal was related to the six-legged turkeys seen around Thanksgiving on
football broadcasts. Other bones include a few vertebrae, arm bones,
and ilia. The animal was probably around 2 meters long and 70 cm
tall at the hips. The name had been floating around since the mid
1990s. Interestingly, the remains were found in a volcanic tuff, which for the non-geology audience members is a former ash bed; thus, a volcano was going off when these five animals died. A volcano puffing away in the background is a cliché of kids' dinosaur books, but it works here. |
|
| "Arkansaurus fridayi" (N.N.) Sattler, 1983 | EK of Arkansas | Originally described as a basal ornithomimid, this animal, based on a partial foot, may actually be closer to basal coelurosaurians like Nedcolbertia. There has been some controversy around it; some have suggested that the remains are a cast of an ornithomimid foot (apparently, in the '70s [when the specimen was found] in Arkansas, there was a spurt of "monster" sightings and other similar things, and according to the hoax hypothesis, the "Arkansaurus" foot is related to this). However, some of the arguments seem contradictory, such as pointing out differences between this foot and that of Ornithomimus; it's not going to be the same, because it's a different animal from a different time and place. That's not a flaw. | |
| ?Asiamericana asiaticus (N.D.) Nessov, 1995 | Coniacian (LK) of Uzbekistan | This tooth genus has had a long odyssey from possible spinosaurid to possible fish to possible relative of Richardoestesia (which itself could be close to a lot of things). The name refers to the fact that similar undescribed teeth are known from North America. | |
| ?"Beelemodon" (N.N.) Bakker, 1997 | ?Kimmeridgian (LJ) of Colorado | This taxon is based on small teeth, which could belong to any of a variety of small Morrison theropod, showing a resemblance to those of most any basal coelurosaur, including compsognathids, basal oviraptorosaurians, and basal deinonychosaurians. | |
| Calamospondylus oweni (N.D.) Fox, 1866 | Barremian (EK) of England | Calamospondylus is a small theropod, based on a missing sacrum, different from that of Aristosuchus. | |
| "Chilantaisaurus" maortuensis Hu, 1964 | Albian (EK) of China | This theropod may be a basal coelurosaurian of some sort, while Chilantaisaurus proper is not. It could be a tyrannosauroid, but this will have to wait until an in-press redescription is published | |
| "Coelosaurus" affinis (N.D.) Gilmore, 1920 (?Arkansaurus) | late Aptian-early Albian (EK) of Maryland | Assigned for a long time to Ornithomimidae, this animal may instead be a more basal coelurosaurian, possibly related to Nedcolbertia and "Arkansaurus". | |
| "Coelurus" gracilis (N.D.) Marsh, 1888 (?Deinonychus) | late Aptian-early Albian (EK) of Maryland | This indeterminate theropod is based on a hand claw similar to that of the contemporaneous Deinonychus. | |
| Euronychodon portucalensis (N.D.) Antunes and Sigogneau-Russell, 1991 | late Campanian-early Maastrichtian (LK) of Portugal | This taxon, possibly related to the troodontids, is based on teeth similar to those of the ubiquitous Paronychodon. | |
| Itemirus medullaris Kurzanov, 1976 | late Turonian (LK) of Uzbekistan | Itemirus is based on an unusual braincase that shows similarities to both tyrannosaurids and dromaeosaurids. | |
| "Euronychodon" asiaticus (N.D.) Nessov, 1995 | Coniacian (LK) of Uzbekistan | Another Paronychodon-type critter, the geographic and temporal separation of this animal from Euronychodon proper reduces the chance it belongs in the same genus. | |
| Paronychodon lacustris (N.D.) Cope, 1876 | Campanian-Maastrichtian (LK) of Montana, Wyoming, and New Mexico | Based on odd, unserrated, and rather common teeth that some have suggested are the deformed teeth of other theropods, Paronychodon is a dubious theropod. | |
| Richardoestesia: Currie, Rigby, and Sloan, 1990 | R. gilmorei (type) Currie, Rigby, and Sloan, 1990 | Campanian-Maastrichtian (LK) of Alberta, Saskatchewan, Montana, and ?Wyoming | Based on a toothy jaw once
referred to Chirostenotes,
which is now known to be toothless,
this animal could be some sort of basal coelurosaurian, and\or the same as
Paronychodon. A tooth
referred to R. isosceles may have something to do with the
seemingly nondinosaurian tooth genus Asiamericana, suggesting
possible Asian relatives. I frankly don't know what to do with this animal. It's more of a tooth genus for a specific type of tooth than anything else. It may have been a bug-eater. Richardoestesia has been the beneficiary of one of the odder nomenclatural disputes of the cladistic era of dinosaur research. It was supposed to have been Ricardoestesia, but an editor of the original document added an 'h" to all occurrences of the name save one use in a caption. Then it got inadvertently stuck in the revised spelling by a first revisor, people weren't sure which to use and got angry on Internet mailing lists, and eventually pretty much everyone decided that the version with the extra "h" should be used. |
| R. isosceles Sankey, 2001 | late middle Campanian-Maastrichtian (LK) of Texas, N.\S. Dakota, Saskatchewan, and Wyoming | ||
| Santanaraptor placidus Kellner, 1999 | Albian (EK) of Brazil | This new theropod is known from ischia, hindlimbs, and three caudals, with associated soft-tissue impressions. A small theropod, with a femur length of 13 cm, it seems to be a rather basal coelurosaurian, possibly related to Ornitholestes. It could be a basal tyrannosauroid; we'll see. | |
| Tanycolagreus topwilsoni Carpenter, Miles, and Cloward, 2005 | Kimmeridgian (LJ) of Wyoming and Utah | This new Morrison theropod is based on most of a skeleton, including a partial skull and most of the limbs. Originally, it was thought to be a specimen of Coelurus, but the two have very different proportions. It would have been about 4 meters long when fully grown, and had a blunt snout. Overall, it was well-proportioned, unlike the hyper long-legged Coelurus or the shrunken-headed Ornitholestes. The Wandering Hand that was first attached to Ornitholestes, then to Coelurus, appears to belong to this animal, along with a premaxilla once referred to Stokesosaurus. Its interesting name has been known informally for several years, but only recently has been published. | |
| Timimus hermani Rich and Rich, 1994 | Albian (EK) of Australia | When first described, this animal was thought to be an early ornithomimid, but, as it's only based on a femur, there isn't enough evidence yet to be sure. | |
| Tugulusaurus faciles Dong, 1973 | Valanginian-?Albian (EK) of China | This small theropod is based on a fragmentary postcranial skeleton including caudals, both "thumbs," and partial hindlimbs. It has been suggested that it may be a chimera, with carnosaurian forelimb material mixed with coelurosaurian (possibly ornithomimosaurian) hindlimbs, but new research indicates that it is a valid if idiosyncratic basal coelurosaurian. Distinctive characters include the forward placement and posterior reduction of the caudal neural arches, and very short 1st metacarpal. It was originally regarded as an ornithomimosaurian. | |
| Wyleyia valdensis (N.D.) Harrison and Walker, 1973 | Barremian (EK) of England | This small theropod is based on part of a humerus (upper arm bone) that was originally described as that of a true bird. | |
| Zapsalis abradens (N.D.) Cope, 1876 | mid-late Campanian (LK) of Montana | This tooth taxon is usually synonymized with Paronychodon, albeit as a large individual. It could be a dromaeosaurid. | |
"Ornitholestidae": I'm reviving the name as a family of convenience for several basal coelurosaurians that seem to group together.
| Taxon or Taxa: | Time\Place: | Comments: |
| Nqwebasaurus thwazi de Klerk, Forster, Sampson, Chinsamy, and Ross, 2000 | mid Tithonian-early Valanginian (LJ-EK) of South Africa | Based on a partial skull and skeleton, Nqwebasaurus (nicknamed "Kirky," because it comes from the Kirkwood Formation) may be a basal coelurosaurian. It has a "killer claw" first hand digit. |
| Ornitholestes hermanni Osborn, 1903 | Kimmeridgian (LJ) of Wyoming | Sometimes considered the same as Coelurus, but actually a much different theropod, Ornitholestes was once pictured as capturing early birds for food, hence the name. The type consists of a partial skeleton and most of the skull. Many recent illustrations picture it with a nasal horn, but further investigation of the type indicates that this was based on a broken and displaced nasal. Ornitholestes has a rather small head for its size, and unusually short lower limb elements suggest it may not have been as good of a runner as other small theropods. In some ways it is similar to allosaurids. It and Proceratosaurus are known for strong heterodonty; the teeth in the front of the skull differ from those behind them by being smaller and more conical in shape. Some researchers put Ornitholestes at the base of Maniraptora. |
| Proceratosaurus bradleyi Huene, 1926 (originally Megalosaurus bradleyi Woodward, 1910) | Bathonian (MJ) of England | Proceratosaurus, though much bigger than Ornitholestes, is very similar. Known from a lower jaw and the bottom two-thirds of a skull, the front tip of which shows the flaring of some sort of nasal prominence (usually interpreted as a horn, but possibly a midline crest), it is currently under restudy. It is also the earliest well-recognized coelurosaurian. |
Tyrannoraptora:
| Taxon or Taxa: | Time\Place: | Comments: |
| Coelurus fragilis Marsh, 1879 | Kimmeridgian (LJ) of Wyoming, Utah, and ?Colorado | Coelurus is known from a good chunk of a postcranial skeleton. This wasn't recognized until 1980, when a study stated that a second species, C. agilis Marsh 1884, was not only the same species but the same individual as the type specimen of C. fragilis. Before this, Coelurus was often confused with Ornitholestes. The type, from a young individual, shows a collection of interesting features, including very long hindlimbs and short but gracile forelimbs. A possible dentary fragment suggests a gracile skull as well. It, along with Tanycolagreus, could be on the line leading to tyrannosaurids. |
Tyrannoraptora i.s.: Two new theropods from the LJ of China have been uncovered; one, known from a partial skeleton, is troodontid-like, while the other, known from the caudal half of a skeleton, is ornithomimosaurian-like.
| Taxon or Taxa: | Time\Place: | Comments: | |
| "Ornithomimus": | "O." minutus (N.D.) Marsh, 1892 | late Maastrichtian (LK) of Colorado | This animal may be an advanced mononykine, but its remains (a partial metatarsus, lost) are too meager for certainty. It could as easily be an avimimid, or another coelurosaurian displaying arctometatarsality. |
| "O." tenuis (N.D.) Marsh, 1890 | late middle Campanian (LK) of Montana | This indeterminate coelurosaur is based on a partial metatarsal. It's usually tossed off as an ornithomimid, but I've also seen troodontid and juvenile tyrannosaurid identifications floated. Whichever it is, you don't have to worry much about it. | |
Maniraptoriformes incertae sedis: Alvarezsauridae: One of the most bizarre groups of dinosaurs, the alvarezsaurids may be flightless avialans, or close relatives of the ornithomimosaurians, or pretty much anywhere in Maniraptora before you hit Aves. The derived members, the mononykines, are very birdlike and have shrunk their arms to almost nothing, retaining only one useful finger per hand in the form of a large stubby clawed thumb, with two other minute fingers hanging off fetchingly, while ironically making the arms very strong. Some sort of digging is implied, but of what is not known, although some evidence suggests that they dug into termite mounds, anthills, and the like. They had big heads with tiny teeth, long skinny running legs, and long thin tails, and are among the smallest known classic dinosaurs.
| Taxon or Taxa: | Time\Place: | Comments: |
| Alvarezsaurus calvoi Bonaparte, 1991 | Santonian (LK) of Argentina | Based on a partial skeleton, this animal was at first considered to a "ceratosaurian", making its current classification somewhat ironic. |
| Patagonykus puertai Novas, 1997 | Coniacian (LK) of Argentina | This animal is apparently transitional between Alvarezsaurus and the rest of Mononykinae. It is known from vertebrae, coracoids, a forelimb, partial hips (weakly opisthopubic [pointing backwards, like in dromaeosaurids and birds]), and hindlimbs. |
Alvarezsauridae i.s.:
| Taxon or Taxa: | Time\Place: | Comments: |
| Achillesaurus manazzonei Martinelli and Vera, 2007 | Santonian (LK) of Argentina | Achillesaurus was a large alvarezsaurid. It is known from partial remains including pelvic and hindlimb bones and caudal verts, and is basal to the mononykines. |
| Heptasteornis andrewsi (N.D.) Harrison and Walker, 1975 | early-mid Maastrichtian (LK) of Romania | Heptasteornis, often lumped with Bradycneme (see under Maniraptora i.s.), is apparently actually an alvarezsaurid (possibly a mononykine), Europe's first. It is based on a partial tibiotarsus that, as with Bradycneme, were first described as belonging to an extinct owl. |
| ?Rapator ornitholestoides (N.D.) Huene, 1932 | Albian (EK) of Australia | Rapator was originally described from an unusual "metacarpal" that bore some resemblance to that of Ornitholestes. Since then, it has bounced among the "carnosaurs," allosaurids, abelisaurids, and "ornitholestids". However, it now seems as though its identity is actually as an alvarezsaurid, its "metacarpal" actually belonging to the strong single finger. |
Mononykinae:
| Taxon or Taxa: | Time\Place: | Comments: |
| Mononykus olecranus Perle, Norell, Chiappe, and Clark 1993 (originally Mononychus Perle et al., 1993) | late Campanian-early Maastrichtian (LK) of Mongolia | Interestingly, remains of this animal (or Shuvuuia; it can get hard to keep track of these little devils) were discovered back in the 1920s by the American Museum of Natural History's Mongolia expeditions, but went unrecognized until the 1990s, when Mononykus was named from other material. It was based on precaudal verts, limbs, parts of both limb girdles, and bones from the back of the skull. Several other individuals are now known. |
| Shuvuuia deserti Chiappe, Norell, and Clark, 1998 | late Campanian (LK) of Mongolia | Known from remains including skull material, this animal is very close to Mononykus. The skull contains numerous tiny teeth. The tail is longer than expected, and the hand had, in addition to the big finger, tiny digits II and III. Skeletally, it may be the best known alvarezsaurid, although its material has at times been confused with contemporaneous Mononykus. |
| Parvicursor remotus Karhu and Rautian 1996 | ?mid Campanian (LK) of Mongolia | This is a very derived (and tiny; femur length shy of 5 cm) mononykine, known from verts, a partial pelvis, and hindlimb material. |
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