Saturday, September 24, 2022

[Herpetology • 2022] Desmognathus valtos • Allocation of Salamandra auriculata Holbrook, 1838, with A New Species of Swamp-dwelling Dusky Salamander (Urodela: Plethodontidae: Desmognathus) from the Atlantic Coastal Plain


Desmognathus valtos  Pyron & Beamer, 2022

Carolina Swamp Dusky Salamander || DOI: 10.11646/zootaxa.5188.6.6

Most swamp-dwelling dusky salamanders of the genus Desmognathus from the Coastal Plain were long treated as a single species (Desmognathus auriculatus) ranging from east Texas to southeastern Virginia. This taxon concept was based on the name Salamandra auriculata Holbrook, 1838 with type locality Riceboro, Liberty County, Georgia and a type series that could not be located by later authors. Recent workers have been unable to locate or verify swamp-dwelling populations from east Texas and western Louisiana, which appear to be extirpated and may not have represented a distinct taxon from co-occurring lineages of D. conanti. Recent molecular phylogenies have supported at least four distinct species-level taxa within D. auriculatus. Populations from the Gulf Coastal Plain in eastern Louisiana, Mississippi, and southwestern Alabama were recently described as D. valentinei Means, Lamb, and Bernardo, 2017 and D. pascagoula Pyron, O’Connell, Lamb, and Beamer, 2022. This leaves two remaining species-level lineages with uncertain taxonomy and nomenclature: D. auriculatus A (Alabama, Florida, and Georgia), and D. auriculatus B/C (Georgia, South Carolina, and North Carolina), both of which occur near the type locality. We recently located a specimen at the Muséum national d’Histoire naturelle in Paris (MNHN 0.4675) that we concluded is one of Holbrook’s syntypes and designated it as the lectotype, but without allocation. Here, we use linear morphometrics to confidently allocate it to D. auriculatus A, bolstered by examination of three historical topotypic collections. This requires a new name for D. auriculatus B/C, which we describe as Desmognathus valtos sp. nov. (suggested common name: Carolina Swamp Dusky Salamander) from Otter Creek, Craven County, North Carolina. Other related and sympatric species of Desmognathus remain to be described from the Atlantic Coastal Plain and adjacent Piedmont of the southeastern United States.

Keywords: Amphibia, Carolina Swamp Dusky Salamander, Desmognathus valtos sp. nov., taxonomy, nomenclature, cryptic species

Holotype (MNHN 2021.0131/RAP0955) of Desmognathus valtos.
 Specimen is an adult (53.1mm SVL), possibly a female based on apparent lack of mental gland and lack of peramorphic or hypertrophied jaw musculature. The holotype exhibits the diagnostic greenish-grey ground color with a reddish-orange dorsal wash, orangish stripe with indistinct margins on the dorsal surface of the tail, yellowish or orangish portholes on the lateral surfaces in three rows, and granular ventral color-pattern with clusters of xanthophores and melanophores interspersed with white flecks and speckles.

Paratype (AMNH A-193889/RAP2294) of Desmognathus valtos.
 Specimen is a small adult (41.2 mm SVL) showing the same diagnostic features as the holotype, with more prominent dorsal color-pattern and lateral white flecking or speckling that is characteristic of younger individuals, with the latter extending noticeably onto the dorsal surfaces.

Desmognathus valtos sp. nov. 
D. auriculatus Holbrook, 1838 (part: see Means 1999; most historical concepts of D. auriculatus included populations from GA, SC, and NC)

Diagnosis: In comparison with the re-description of Desmognathus auriculatus (Holbrook, 1838) by Means et al. (2017), D. valtos is a moderately-sized Dusky Salamander (17.2–62.4mm SVL for transformed specimens), typically with a dark greenish-grey ground color and orangish wash on the dorsal surfaces (Fig. 2). Smaller individuals often have visible remnants of orangish or reddish paired larval spots on the dorsum; differentiation between dorsal and lateral color pattern is typically absent in D. auriculatus, and larval patterning is usually obscured by darkening in even the smallest specimens. Differs significantly in overall size and shape from D. auriculatus, the greatest difference being proportionally longer torsos (longer AG). Tail is thick, girthy, and long, up to 106% SVL, typically less keeled than D. auriculatus, but still flattened at the terminus. Dorsal surface of tail typically exhibits a yellowish or orangish stripe with indistinct margins even in larger individuals (Fig. 2–5); such stripes are usually less colorful and prominent in D. auriculatus, particularly older specimens. Ventrolateral porthole markings with whitish, yellowish, orangish, or reddish pigment may occur in up to three rows (see Pyron et al. 2022b and references therein), but these are generally less prominent than in D. auriculatus. Ventral color pattern is typically relatively bright and granular, consisting of interspersed flecking of darkened melanophores, lighter xanthophores, and whitish speckling, while in D. auriculatus, “the belly is unmistakably black but may be densely peppered with small whitish or silvery speckling (Fig. 14c)” (Means et al. 2017). 

Etymology: The specific epithet is a non-Latin noun used in apposition, from the Greek váltos (βάλτος) for “swamp,” in reference to the primary habitat of the species. We suggest the common name “Carolina Swamp Dusky Salamander.” 
 R. Alexander Pyron and David A. Beamer. 2022. Allocation of Salamandra auriculata Holbrook, 1838, with A New Species of Swamp-dwelling Dusky Salamander (Plethodontidae: Desmognathus) from the Atlantic Coastal Plain. Zootaxa. 5188(6); 587-595. DOI: 10.11646/zootaxa.5188.6.6