On occasion, systematists feel the need to revise the taxonomy of various species, placing species into new genera, or lumping them in with other species in earlier-named genera. This is generally supported by phylogenetic analyses, but sometimes it involves an argument of differentiation based on physical differences, or mere opinion on the basis of particularly “important” features (generally autapomorphies). This can have several results, but the most common is that a systematist will erect a new genus for a “special” species formerly placed in another genus. Ignoring the question of what a genus is, we wonder what the answer to the question “What is the value of a generic assignment?”
I am of two minds: There is a principle of originalism, but also of “sense.” The former tends to be the most prevalent, although the second tends to rear its head time to time.
The principle of originalism goes: generic or specific assignments without systematic support for alternate hypotheses should be maintained. Under this philosophy, Brachiosaurus Riggs (1903) should include the type species (Brachiosaurus altithorax Riggs, 1913) as well as additional species, Brachiosaurus brancai Janensch, 1914, even if further analysis argued that Brachiosaurus brancai should be placed in a different genus (in this case, Giraffatitan Paul, 1988, see Taylor, 2009), so long as that analysis does not show either species to be closer to a species belonging to a different genus placed elsewhere phylogenetically.
Now, were brancai placed in a different position systematically, closer to another taxon than altithorax, this would change and Giraffatitan might be supported. The reason why this is untenable is because no analysis currently supports brancai as closer to another non-Brachiosaurus species; Taylor (2009) reasons this due to a large number of analyses lumping both species into a single unit for phylogenetic assessment, but also when used, only brancai is ever analyzed, but not altithorax. Testing this, Taylor found low support (if any) placing either species separately, but this is ambiguous according to Taylor. Nonetheless, until such an analysis is forthcoming with strong support, originalism dictates use of Brachiosaurus as the container for brancai, not Giraffatitan.
But on the other hand, there is the “sense” argument: Due to a taxonomic quirk known as priority and the large number of names present in the literature, some of them fairly obscure, names tend to get replaced from out of left field (as it were). This occurred with Diceratops Lull vide Hatcher (1905) [n1], which was later found to be preoccupied with an insect and renamed Nedoceratops (Ukrainsky, 2007); owing to its obscurity, the name was unknown when Mateus (2008) attempted to replace the name with Diceratus, a fact that Ukrainsky rejected using his own work in a more widely-known venue (Ukrainsky, 2009). This has led to a relatively convoluted synonymy list for whatever container holds hatcheri Lull vide Hatcher (1905), largely because the species has also been subsumed into Triceratops, sometimes as a synonym of one of its other species (see Scannella & Horner, 2010; Farke, 2011). Nonetheless, sense argues that we follow the latest assignment when all the details, even in the case of phylogenetic analysis, are applied. Farke (2011) argues against the opinion of Scannella and Horner (2010) by noting a large number of features that distinguish Nedoceratops hatcheri from Triceratops, thus permitting us to support the assignment.
This can have issues: What were to happen, say, if Nedoceratops does belong within a group of ceratopsians that includes Triceratops horridus the type species) and Triceratops prorsus? Originalism might imply we should then have to make a choice between retaining Nedoceratops and distinguishing all species into their own equivalent “genus” containers (meaning a name would be coined to contain prorsus), or we subsume all others into Triceratops (as Scannella and Horner, 2010 chose), regardless of morphological ambiguity (Farke, 2011).
ICZN rules argue that the earliest valid name has priority over any other, and even a different animal named the same should have its name changed. This results in a need for a replacement, and Ivie et al. (2001) provided this in the case of Megapnosaurus. Noting that the name Syntarsus (for Syntarsus rhodesiensis Raath, 1969) was preoccupied by a beetle, Ivie et al. (2001) erected a new name for rhodiensis, creating Megapnosaurus rhodesiensis. However, the name they chose has problems. Ivie et al. coined the name from the Greek words μεγα (mega, “big”) and ‘απνοος (hapnoos, “non-breathing”), to create “big dead lizard.” Appearing in an entomology journal, this name was viewed as an affront on several levels, not just because of an entomologist renaming a taxon when the original author is generally granted this right (Mike Raath being available at the time), but also in the choice of terms, where a “big dead lizard” seems to be a fairly non-benign way to look at dinosaur-based paleontology. Ivie, in a message to the Dinosaur Mailing List, argued that it “was a joke,” but despite this, the name sticks.
The name has become something of a sore-spot. The general consensus has been to ignore it, and use Syntarsus anyways (e.g., Carranno & Sampson, 2008), or ignore it and use Coelophysis instead, to which Syntarsus has been synonymized by others (Bristowe and Raath, 2004; Bristowe et al., 2004; Yates, 2005). The latter has the benefit of ignoring the problem in a legitimate manner, but it runs afoul of the issue of originalism; the former runs afoul of ignoring the ICZN entirely, a subject of some oddity as both authors who did this also seek to employ the ICZN in arguing for the correct genus of Majungasaurus crenatissimus (Krause et al., 2007) or the type specimen of that species (Carrano et al., 2009).
Nonetheless, the issues above bear scrutiny. Should we employ a “sense” model, we apply a subjective, and fairly non-scientific “feels good” impression. The emotional concerns invested in such issues as Megapnosaurus (which I am generally opposed but argue is the appropriate name when rhodesiensis is considered non-Coelophysis), Giraffatitan (to which I am opposed to using for brancai so long as no good analysis is published supporting any reason the “genus” is useful systematically), or Nedoceratops (which analysis supports separately from other species, but which may get lost due to concerns over the “extent” of a genus) leads us down a metaphorical obstacle course, each decision placing a new barrier in the way and making the course longer and more complicated (just like any evolving rulebook).
I am hesitant about using Megapnosaurus, but I think that if we must treat Syntarsus rhodesiensis Raath, 1969 separately from Coelophysis, we should use it (I do not think the naming authors gave full faith to Mike Raath to re-select his own nomenclature). Certainly the same would be true of Giraffatitan, which has as its only current value the “sense” that brancai is different enough from altithorax to warrant it, a diagnostic separator that has yet to see the light of analysis.
Systematic originalism is, in the end, I think, the better of the two options, as it leaves less subjectivity to the taxonomist. It may require us swallowing our pride and perhaps our esteem, but we are ostensibly scientists, even if we occasionally practice art (nomenclature).
[n1] John Bell Hatcher is credited with the name Diceratops hatcheri by Richard Swan Lull largely due to Hatcher’s work intending to publish said genus. Hatcher, however, died before completing a monographic work, which O. C. Marsh began to finish before he, too, succumbed. Richard Swan Lull, in better health, completed the monograph, then separately published the portion of the work erecting a new taxon, using Hatcher’s intended name, and renaming the species in Hatcher’s honor. The “vide” appellation is an honorific from Lull in reference to the work both men labored on.
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