Old Names for Old Bones

Before writing up a big review post for tomorrow, I thought I'd address a request I've gotten a few times, most recently over on my deviantArt page. I've written a few times about old/disused names that have fallen out of fashion in paleontology with little reason (or for reasons that can't really be supported by evidence). In fact, a lot of these 'quaint' or 'old-fashioned' sounding names should really be considered just as valid today as when they were coined.

Now, keep in mind that at least in cases of priority for family-level names, it has been argued that anything goes, because researchers are not necessarily using these names as 'families' under the ICZN but identical clade names that fall under no governing code. In my opinion this is a bit of a cop-out, and a bit hypocritical when espoused by people who would otherwise argue that nomenclature needs to do its best to reduce confusion. I agree with some PhyloCode proponents that, for this reason, endings like -idae should be avoided in clade names at all costs, or at least, those names should be defined in such a way that they roughly correspond to their traditional family name homonyms.

There has been a general tendency in the past few decades to somewhat arbitrarily replace names based on fragmentary taxa with those based on more complete (or simply more famous) taxa. This, again IMO, ultimately negatively impacts stability of nomenclature, despite the fact that many of these 'replacement' names have since come into such common use, coinciding with widespread use of the Internet, that changing them back now gives a false impression of instability. Luckily, some more recent research is beginning to correct a few of these mistakes of recent history. Megalosauroidea (a name based on a fragmentary taxon) had long been replaced by Spinosauroidea (a name based on a different but more apomorphic fragmentary taxon) in the literature, but several recent papers by Benson and colleagues have argued fairly successfully for a reversal of this trend and a return to valid priority.

In a way, it's a shame that the PhyloCode will not give priority to the original author of a name, but rather to the author of its definition, essentially enshrining unjustified replacement names like Coelophysidae in favor of older names like Podokesauridae, robbing the original authors of their rightful credit. It would upset temporary stability (or rather, reverse prior results of instability) but ultimately make more sense to automatically give preference to the older names and their authors, even if they aren't converted to clades immediately when PC goes into effect.

Anyway, here I'll give a brief rundown of some disused names that should still by all rights be considered valid senior synonyms of other names. I'll also throw in a few genera that may have a claim to seniority over more widely used, better known names. Note that this later bit is a completely separate issue--seniority for family-level names is straightforward. At the genus or species level, as I've argued before, often names are ignored as unofficial "nomina dubia". Nomen dubium refers to a name based on a specimen which lacks key apomorphies and cannot be distinguished from two or more similar specimens. However, in many cases I believe stratigraphy itself should be taken into account. If a bone fragment is obviously from a allosaurid theropod, and current evidence only supports the presence of one other such theropod in its stratigraphic level, parsimony dictates they should be considered the same taxon. If and when evidence is found to support the presence of multiple allosaurids in that formation, then and only then can non-diagnostic allosaurid remains be declared nomina dubia.

One more note on nomina dubia: the ICZN does not support the existence of this concept (and as far as I know, neither does the PhyloCode). According to the ICZN, if a type specimen is found to be non-diagnostic relative to more complete specimens, the name should not be ignored--rather, one of those more complete specimens should become the neotype of the oldest available name. So, for example, Deinodon (see below) should not simply be ignored as non-diagnostic relative to Gorgosaurus and Daspletosaurus and then ignored; rather, scientists should have arbitrarily chosen one of those two specimens to become the neotype, removing the validly published name from poor material and leaving the poor material nameless. This is, of course, almost never done, especially among paleontologists, where making sure your name is the one that sticks has historically been a higher priority than eliminating nomenclatural clutter (whether or not scientists who name scrappy material have more of a right to their names to persist than those who describe complete specimens is another story).

Okay, enough of an intro. Here are some old names, and quick examinations of whether or not they should be resurrected:

Families:
Podokesauridae (Huene 1916) is perhaps the classic example of a valid taxon name abandoned for no good reason. In use up until the early 1990s, the name was suddenly changed to Coelophysidae (Nopcsa, 1928) when Holtz and Sereno began to fist include this group in phylogenetic analyses. As far as I know no justification for this was ever given, but I don't have these initial papers to check. At any rate, the type specimen of Podokesaurus has been distinguished from Coelophysis by researchers going back to Colbert in the 1950s, so it is by definition not even a nomen dubium. There is therefore no justification to ignore this name in favor of Coelophysidae/Coelophysoidea etc.

Metriacanthosauridae (Paul 1988) is another case like Podokesauridae where a perfectly valid name based on diagnostic material was arbitrarily replaced by its junior synonym, Sinraptoridae (Currie & Zhao 1994) among most researchers. Nobody doubts the diagnosibility of Metriacanthosaurus as far as I know, and as discussed, this doesn't matter anyway.

Megalosauroidea (Huxley 1869), as discussed above, is a senior synonym of Spinosauroidea (Stromer 1915). Again, Spinosauroidea gained broad acceptance in the early '90s, but several recent papers have been effective in reversing this baffling trend to arbitrarily ignore a widely used name with a history almost as long as dinosaur paleontology itself.

Omnivoropterygidae (Czerkas & Ji 2002) is another case where a once-ignored name is starting to gain traction again in favor of its junior synonym Sapeornithidae (Zhou & Zhang 2006). Both Greg Paul and Tom Holtz have used the correct name in recent popular works, though Sapeornithidae still crops up in the technical literature. This name is an even better illustration of the Czerkas problem. People who favor the junior Epidendrosaurus over Czerkas' senior Scansoriopteryx can at least fall back on the online vs. print publication excuse (though the ICZN is clear and unequivocal on the matter). In the case of this family name (neither have yet been defined as clades), Czerkas' name has 4 years of priority and is still ignored. Let's not beat around the bush--people disagree with Czerkas' conclusions and don't like the way he has (validly if unpopularly) published many of his taxa, and they express this distaste by ignoring his taxonomy. The ICZN has no provision to replace names created by unpopular scientists.

Ornithodesmidae (Hooley 1913) has priority over the better-known Dromaeosauridae (Matthew & Brown 1922). The scrappy type specimen of Ornithodesmus, though initially (correctly) identified as a primitive bird, was soon confused with the much better remains of the pterosaur now known as Istiodactylus. Hooley named Ornithodesmidae as a family of pterosaurs, but it became a theropod family when Ornithodesmus was again recognized as a maniraptoran in 1993. Naish & Martill (2007), as well as Makovicky & Norell (1995), and Mortimer (online) have shown that Ornithodesmus falls into the same family as Dromaeosaurus. So, unless Dromaeosauridae is re-defined to include only Dromaeosaurus and a few closely related taxa (~current Dromaeosaurinae) or trated as a synonymous but differently goverened clade (under the future PhyloCode), Ornithodesmidae has clear priority of name under the ICZN.

Atlantosauridae (Marsh 1877) has clear priority of name over the more well known Diplodocidae (Marsh 1884), and Hay (1902) argued that it has priority over Amphicoelidae (Cope 1877). Atlantosaurus is almost certainly a synonym or close relative of Apatosaurus, and while it may be a real nomen dubium in relation to the various species of contemporary atlantosaurine (=apatosaurine) sauropods, it is definitely a member of this group, and thus higher taxon names should be used accordingly. Even if a taxon is a nomen dubium, there is no reason to change higher taxa names based on it if it can be confidently classified at the 'family' level (as is the case with Ceratopsidae). Again, Atlantosauridae has not yet been defined as a clade, so if Diplodocidae is defined first under parallel systems such as PhyloCode, a situation will arise where Atlantosauridae is valid under one code but not the other--Diplodocidae will be a valid name but for a clade, not a family. Olshevsky (1991) incorrectly labelled Atlantosauridae a nomen oblitum (forgotten name). The ICZN states that to be a nomen oblitum, a name must not be treated as valid in the scientific literature after 1899. However, Atlantosauridae was in use in papers by Steel (1970) and Nowinsky (1971) well into the late 20th Century.

Deinodontidae (Cope 1866) is a slightly more complicated case than the above. It was in clear, widespread use through the mid 20th Century (as in Maleev 1955) and almost always treated as the senior synonym of Tyrannosauridae (Osborn 1905). However, Russel (1970) argued that Deinodontidae be abandoned, because he considered the type specimens of Deinodon (isolated teeth) not diagnostic, rendering the name a nomen dubium. However, the teeth are clearly diagnostic at the family level and possibly even genus and species, as they must have come from either Daspletosaurus or (more likely) Gorgosaurus, and the rocks those dinosaurs come from are well enough sampled to rule out the presence of a third large tyrannosaur species unless such compelling evidence is found. Similarly, it is questionable whether or not the pertinant ICZN rules allow for abandoning a name due to a dubious type genus. Even if this is the case, it is only followed sporadically in the literature, and many family names remain in use that are based on dubious type material, including Hadrosauridae, Ceratopsidae, and Troodontidae (the latter is also based exclusively on teeth of questionable diagnosability at the genus and species levels). Olshevsky (1991) recognized this, but argued that the name is still invalid because Cope initially spelled it Dinodontidae, and the name Deinodontidae was an emended spelling not published until 1914, after Tyrannosauridae. He concluded that therefore Deinodontidae (with an e) is a junior synonym and Dinodontidae (no e) is a nomen oblitum. However, Olshevsky's argument is incorrect because the ICZN clearly mandates that any family names based on misspellings or unjustified spelling changes of their type genus (Cope spelled the name Dinodon) can and must be emended by any subsequent revisor, and that this does not change the original authorship or date of the name (ICZN Article 35.4.1). Also, note that even if Deinodontidae and Deinodontoidea are ignored, several studies have found Coelurus fragilis to be a "tyrannosauroid", and so the next available name for that group after Deinodontoidea is Coeluroidea (Marsh 1881).

Trachodontinae (Lydekker 1888) may have priority over Lambeosaurinae (Parks 1923). As discussed below, the Trachodon holotype teeth may be diagnosible to subfamily level, as some researchers have suggested that they belong to a 'lambeosaurine' rather than a 'hadrosaurine/saurolophine'. If this is the case, even if Trachodon is itself a real nomen dubium (which it probably is), the family name would still carry priority.

Titanosauridae (Lydekker 1885) is, despite being based on a possible nomen dubium, a valid taxon name. However, this situation is complicated for a new reason: the 'family' has proven so large that most researchers now divide it up into several families. If multiple families of titanosaur are used, Titanosauridae itself (but not Titanosauroidea) must be restricted to its dubious type species. This is analogous to the Ornithodesmidae situation described above: if 'dromaeosaurids' were divvied up into several families (Microraptoridae, Velociraptoridae, Saurornitholestidae, Dromaeosauridae), then Ornithodesmidae would still be valid but monotypic, and probably (rightly) fall out of use again.

Hylaeosauridae (Nopcsa 1902) is a senior synonym of Polacanthidae (Weiland 1911), but this is another situation where a name is only valid under certain classifications. Some older classifications placed the group as separate from Ankylosauridae and Nodosauridae, or as a subfamily of either (as Polacanthinae). In these cases, Hylaeosauridae/inae has priority. However, some new studies show the 'polacanthines' the be nested within nodosaurs, and to be possibly paraphyletic. Nodosauridae (Marsh 1890) has priority over both Polacanthidae and Hylaeosauridae, so both names are sunk either way.

This last one isn't a dinosaur group, but is quite an odd situation. As it turns out, Pterodactyloidea (Meyer 1830) has, according to the principal of coordination, priority over the widely-used pterosaur group Ctenochasmatoidea (Nopcsa 1928). Note that this is a different taxon than Pterodactyloidea (Pleininger 1901), traditionally labeled as a suborder. But... they have the same name. This isn't technically a problem because the later Pterodactyloidea, named as a group above the rank of superfamily, is outside any governing code, and practically, nobody uses the superfamily Pterodactyloidea (or Rhamphorhynchoidea, for that matter). But those have priority over other names, which makes them more valid than the suborder name, which can easily be replaced with a new name the way Segnosauria was replaced with Therizinosauria (neither of them governed by the ICZN, so anarchy applies).

Genera and species:
Deinodon horridus (Leidy, 1866) currently appears to be a real nomen dubium, as it is based on deinodontid teeth from the Judith River Formation. I say currently because its status depends on the currently messy taxonomy and stratigraphy of the various specimens/species assigned to Daspletosaurus. Daspletosaurus is not present in the Judith River formation sensu stricto, and is generally known from younger deposits than the chronologically-overlapping albertosaurine species Gorgosaurus libratus. However, specimens that may or may not be Daspletosaurus are known from such a wide temporal and geographic range that it's possible these teeth could belong to it (or a similar tyrannosaurine) instad of Gorgosaurus. Additionally, if it ever is demonstrated to be possible to distinguish between albertosaurine and tyrannosaurine teeth, Deinodon can and should be ressurected to replace one of these two genera. Note that Matthew & Brown 1922 considered both G. libratus and Albertosaurus sarcophagus to fall within the genus Deinodon--this is dependent on subjective lumping vs. splitting (if libratus and sarcophagus are placed in the same genus, and Deinodon=Gorgosaurus, Albertosaurus is also a junior synonym of Deinodon), and ignores the possibility that Daspletosaurus represents the true skeleton of Deinodon. For now, Deinodon must be considered a nomen dubium.

Trachodon mirabilis (Leidy 1856) was named for isolated teeth of a hadrosaur (and some mixed in from a ceratopsian), Also from the Judith River formation. As mentioned above, they may be diagnosable to the level of Lambeosaurinae (=Trachodontinae?). I'm not knowledgable enough about hadrosaurs to know if this species might be currently valid based on stratigraphy. As far as I'm aware, no definite remains of named lambeosaurines are known from the Judith River formation, though this spans a great deal of time and in places overlaps with the Oldman and Dinosaur Park formations of Canada, which contain numerous lambeosaurs at different and better-studied stratigraphic levels. If anybody knows approximately which portion of the Oldman/Dinosaur Park group this part of the Judith River corresponds with, we might be able to find an answer.

Antrodemus (Leidy 1870) has long been recognized as a possible synonym of Allosaurus (Marsh 1877). In fact, I remember making a note 'alos known as Antrodemus' in one of my dinosaur books in the '80s (sticklerism arises early!). As Mickey Mortimer points out on the Theropod Database, Chure (2000) noted that the species of Allosaurus Antrodemus comes from can't be determined, but Chure doesn't consider it a synonym of Allosaurus because it comes from an unknown quarry. I would agree with this, as long as there are multiple genera of allosaurids recognized in the Morrison (i.e. Saurophaganax). If, however, one were to synonymize Saurophaganax and Allosaurus, the name for this genus must then become Antrodemus, no matter how many diagnosable species it contains (Antrodemus valens, the species, would still be a nomen dubium).

I'm sure there are other dinosaurs that could be added to this list, and I may try to do a 'part 2' someday. I've discussed the situations about the Lancian forms Manospondylus, Agathaumas, and Thespesius before.

Stay tuned for something a little less arcane, nitpicky, sticklerish, and taxonomical. The next post will be (gasp!) an unabashedly positive review of possibly the best dinosaur show ever to make it to air.