Proposal (860) to South American Classification Committee
Create an English name for Sclerurus obscurior
Effect on SACC: This would create an English name for the South American forms that we have voted to treat as a separate species from Middle American Sclerurus mexicanus. Importantly, this is likely a temporary name, because all sentiment from previous proposals (SACC 603, SACC 752) indicates that we think that broadly defined S. obscurior contains multiple species that will be recognized as such with publication of additional data.
Background: See proposals cited above. The bottom line is that we have voted to recognize a minimal 2-way split that recognizes the two northern, Middle American forms (nominate mexicanus with pullus) as a separate species from the largely South America forms, for which the oldest name is S. obscurior.
This is a unusual situation because: (1) one of the daughter species, Sclerurus mexicanus, is exclusively Middle American, thus under NACC purview, and so our role is advisory only, and (2) all evidence so far strongly suggests that the two daughter species, Middle American and South American, both consist of two or more species that would be recognized if more published data were available. Thus, whatever we decide here likely represent temporary “place-holder” English names with limited longevity. Therefore, I don’t see a reason for putting too much effort into this – it’s just something we have to do to move one step forward by implementing the minimal 2-way split. Perhaps more important is thinking ahead in our choices for the temporary names for the consequences for the eventual names (see Cooper & Cuervo 752 for possibilities).
I recommend looking at the map in SACC 752 as a starting point. Our split breaks the two species in E. Panama, where pullus and obscurior meet.
Because all component taxa have been treated historically as a single polytypic species, S. mexicanus, that was not given a composite name until Meyer de Schauensee (1966) [or more likely Eisenmann 1955 – but I don’t have access to my copy to check- can someone check] called it Tawny-throated Leafscraper (subsequently modified to Leaftosser). Ridgway (1911) and Cory & Hellmayr (1927) provided English names for each subspecies but not for the composite species; those names (with Sclerurus or Leaf-scraper as “last” names) were:
S. m. mexicanus: Mexican
S. m. pullus: Dusky
S. m. anomalus: Panama (now treated as synonym of pullus)
S. m. obscurior: Pacific
S. m. andinus: East Andean
S. m. peruvianus: Peruvian
S. m. macconnelli: Guianan
S. m. mexicanus: Mexican
S. m. bahiae: Bahia
In anticipation of future splits, I suggest that these names are off limits to prevent confusion when some or all of these are elevated to species rank. Also, “Tawny-throated” needs to be retired for our informal SACC guideline of avoiding use of parental name for a phylogenetic daughter (and NACC’s now formal guidelines currently under our consideration).
That doesn’t leave much to work with. I don’t see any consistent plumage differences between the two groups. In the absence of alternatives, my limited imagination sees only two possibilities: Northern vs. Southern, and Middle American vs. South American. I lean slightly towards Middle American and South American as providing more information. With respect to congeners, broadly defined S. obscurior has the largest range of any South American Sclerurus (as does broadly defined mexicanus for Middle America). The bad aspects of either pair of names are too obvious to elaborate. Given that either set will likely have a mercifully short shelf-life, I recommend we not get too worked up about the pros and cons. That said, if anyone has a better suggestion, please come forth in your comments.
Given my own very slight lean, let’s make the voting as follows: YES = “Middle American” and “South American”, and NO = “Northern” and “Southern” (or something else). Our suggestions for S. mexicanus would be advisory-only.
Van Remsen, June 2020
Comments from Jaramillo: “NO. Use North American and South American instead of Middle American. I think North American is formally more correct than Middle American.”
Comments from Zimmer: “YES. Van’s reasoning that these names are almost certainly “placeholders” is well taken, and therefore, the idea that the English names used by Ridgway and Cory & Hellmayr should be held in reserve in anticipation of future splits makes perfect sense. Given that what we are currently dealing with is a two-way split, with one daughter restricted to Middle America and the other, with a range that is 99% restricted to South America, suggests to me that the proposed names of “Middle American Leaftosser” and “South American Leaftosser” are the way to go.”
Comments from Schulenberg: “YES, I can't wait for AOS NACC and SACC to get to the end point of the species-level classification for this group. Middle American and South American are lame, but I'll vote for them for now, since that's easier than proposing novel, equally lame names that - we hope - will not have a long shelf life anyway.”