Reappraisal of the status of two recently described western Atlantic species of sand crabs (Anomura: Albuneidae)

Abstract Evidence is provided to support the synonymy of two species of sand crabs (Anomura: Albuneidae). Zygopa lalanai Ortiz, 2015 is a synonym of Zygopa michaelis Holthuis, 1961 and Lepidopa boykoi Ortiz, Tello-Musi and Morales-Moreno, 2018 is a synonym of Lepidopa benedicti Schmitt, 1935. Each of the recently described species was based on a single specimen collected well within the range of their respective senior synonyms.


INTRODUCTION
Two species of sand crabs from the Caribbean and the Gulf of Mexico were recently described by Manuel Ortiz and colleagues (Ortiz, 2015;Ortiz et al., 2018).A review of these publications shows that both species are synonyms of previously described species known from these regions.Zygopa lalani Ortiz, 2015 is a synonym of Zygopa michaelis Holthuis, 1961 and Lepidopa boykoi Ortiz, Tello-Musi and Morales-Moreno, 2018 is a synonym of Lepidopa benedicti Schmitt, 1935.Evidence is presented herein to support these synonymies.
Remarks.Zygopa lalanai was purportedly distinguished from Z. michaelis by the shape of the ocular peduncles (tapered vs. rounded distally; Fig. 1B vs. 1D), but this is the only character that appears to differ between the holotype (and only specimen) of Z. lalanai and the numerous known specimens of Z. michaelis (see Boyko, 2002).The carapace groove (CG) pattern is the same in both species, as evidenced by a comparison of the photographic fig.Zygopa michaelis is known from both coasts of Florida, USA, to Brazil, in 4.0-73.2m depth; the holotype of Z. lalanai was collected off Cuba in 6-8 m depth, a locality well within the known range of Z. michaelis.
As the only apparent difference between Z. lalanai and Z. michaelis is in the degree of the tapering of the ocular peduncles, this must be considered intraspecific variation, possibly age, size, or even preservation related, and the two species are synonymous.Zygopa at present contains only two valid species: Z. michaelis and Zygopa nortoni Serène and Umali, 1965 (known from the Philippines and New Caledonia, ranging to 60 m depth) (Boyko, 2002).

Status of two western Atlantic species of sand crabs
Nauplius, 31: e2023021
Remarks.Ortiz et al. (2018) distinguished the holotype and only specimen of L. boykoi from other species in the genus found in the Gulf of Mexico and Caribbean in their key to species using the following set of characters: "pedúnculos oculares rectangulares; con corneas presentes en sus ángulos basales internos; tacón del dactilo del pereópodo I redondeado; borde ventral distal del dactilo cubierto de setas largas cuvadas."However, none of these are unique to this specimen.
Rectangular ocular peduncles are found on several species in the genus, including L. benedicti and the pigmentation found in the proximomesial corner of the ocular peduncles (e.g., Fig. 3A) is only an artifact of preservation (see Remarks under various species in Boyko, 2002 where dispersal of pigments is noted).It is unclear what "tacón del dactilo del pereópodo I redondeado" (heel of pereopod dactyl I rounded) means as there is no heel present on pereopod I; it is possible the original description meant to refer to pereopod II, which does have a rounded heel as also seen in L. benedicti and several other species of Lepidopa.The notation of long curved setae on the ventral edge of the dactylus (which dactylus the descriptions refer to is not clear, perhaps all of them) is not diagnostic, as this feature is found in all species in the genus.The drawings of the whole animal (e.g., Ortiz et al., 2018: fig. 1b and inset) are of limited utility and comparison of the photo of the dorsal view (Ortiz et al., 2018: fig.5a, c), despite its suboptimal angle and small size, clearly shows that at least some of the carapace grooves (CG) are inaccurately placed or excluded from the line drawings.The most glaring error is that CGs 6 and 7 are placed much too posteriorly on the carapace in the line drawing (Fig. 2A vs. 2B herein).The line drawing shows an incomplete submarginal groove which is also seen in L. benedicti; this is not visible in the photograph of Ortiz et al. (2018).The drawings of the individual parts of the holotype appear more accurate renderings, although fig.4e of pereopod III clearly shows that the dactyl of this same appendage is drawn inaccurately in fig.1b and the tip of the heel in fig.4f appears broken (Fig. 3B).Overall, the shape of the dactyli of pereopods I-IV matches those of L. benedicti (Fig. 4A-C vs. 4D, E).
Lepidopa benedicti is known from the central Atlantic coast of Florida, USA, and Gulf of Mexico south to Veracruz, Mexico, in up to 3 m depth (Boyko, 2002).The holotype of L. boykoi was also collected from the littoral zone of Veracruz, Mexico, at the southernmost known edge of the species' range.When all the above similarities, both morphological and distributional, are considered, L. boykoi is clearly a synonym of L. benedicti.The author of the present note profoundly regrets to synonymize this species (for obvious reasons), but it seems unavoidable.

DISCUSSION
Although it is regrettable that these two recently described species must enter into synonymy, this highlights an important recommendation when it comes to describing new species of albuneids and, indeed all species: it is inadvisable to describe a new species from a single specimen, especially when the specimen occurs within the range of known congeners unless the specimen exhibits multiple distinctive characters that clearly distinguish it from all previously described species in the genus (e.g., Boyko, 2020).

Status of two western Atlantic species of sand crabs
Nauplius, 31: e2023021 borrow the type material from the Colección Nacional de Crustáceos, Instituto de Biología, Universidad Nacional Autónoma de México (CNCR).Images were constructed in Adobe Photoshop. SYSTEMATICSOrder