North American Taxa Research Articles

Tuberona nom. nov., a replacement name for Tuberocandona Külköylüoğlu et al., 2023 (Crustacea, Ostracoda)

The name Tuberocandona has been applied to two different genera of Ostracoda, first to a fossil genus described in 1995 from Europe and then to an extant genus reported in 2023 from North America. Because the name of the European genus takes precedence, a new name is proposed for the North American taxon.

Phylogeny and taxonomy of the genera of Erysiphaceae, part 3: Cystotheca

ABSTRACT This contribution is part of a series devoted to the phylogeny and taxonomy of powdery mildews, with an emphasis on North American taxa. An overview of Cystotheca species is given, including references to ex-type sequences or, if unavailable, proposals for representative reference sequences for phylogenetic-taxonomic purposes. The new species C. mexicana is described, based on Mexican collections on Quercus glaucoides × Quercus microphylla and Quercus liebmannii × Q. microphylla. Cystotheca lanestris is reported for the first time worldwide on Quercus laceyi (Collected in Mexico) and on Q. toumeyi (collected in Arizona, USA). Cystotheca lanestris on Q. agrifolia and on Q. cerris is reported for the first time in Mexico. Epitypes with ex-epitype sequences are designated for Cystotheca wrightii, Lanomyces tjibodensis (= C. tjibodensis), Sphaerotheca kusanoi, and S. lanestris (C. lanestris).

Widespread gene flow following range expansion in Anna's Hummingbird.

Anthropogenic changes have altered the historical distributions of many North American taxa. As environments shift, ecological and evolutionary processes can combine in complex ways to either stimulate or inhibit range expansion. Here, we examined the role of evolution in a rapid range expansion whose ecological context has been well-documented, Anna's Hummingbird (Calypte anna). Previous studies have suggested that the C. anna range expansion is the result of an ecological release facilitated by human-mediated environmental changes, where access to new food sources have allowed further filling of the abiotic niche. We examined the role of gene flow and adaptation during range expansion from their native California breeding range, north into Canada and east into New Mexico and Texas, USA. Using low coverage whole genome sequencing we found high genetic diversity, low divergence, and little evidence of selection on the northern and eastern expansion fronts. Additionally, there are no clear barriers to gene flow across the native and expanded range. The lack of selective signals between core and expanded ranges could reflect (i) an absence of novel selection pressure in the expanded range (supporting the ecological release hypothesis), (ii) swamping of adaptive variation due to high gene flow, or (iii) limitations of genome scans for detecting small shifts in allele frequencies across many loci. Nevertheless, our results provide an example where strong selection is not apparent during a rapid, contemporary range shift.

A molecular phylogeny of the European nesticid spiders (Nesticidae, Araneae): Implications for their systematics and biogeography

Nesticidae is a small family of spiders with a worldwide distribution that includes 15 genera and 272 described species. Seven genera and 56 species are known from Europe, distributed from the Iberian Peninsula to the Caucasus and the Ural Mountains. Most of these European species are cave dwellers and many of them are troglobites. In this study we present the first molecular phylogeny of the family Nesticidae in Europe with a wide geographical sampling across the continent. In our analysis the European nesticid fauna is well represented, including six genera and 40 of the 56 currently accepted species including the type species of all sampled genera. We have included in the analysis representatives of the North American and Asian fauna to test the monophyly of the European species and the phylogenetic relationships of European lineages. Phylogenetic relationships were reconstructed using maximum likelihood and Bayesian inference. As part of our Bayesian analyses, we also dated the phylogeny using two approaches, one based only on fossil calibrations and one that included an additional biogeographical constraint.Our results show paraphyly of the European nesticids with respect to the Asian and North American taxa. We recover four main lineages within Europe. These four European lineages and all European genera have 100% bootstrap support and high posterior probability support in the BEAST2 analysis. The Typhlonesticus lineage is the earliest branching clade present in Europe and includes seven species, the five currently accepted species plus T. parvus from Bosnia and Herzegovina and T. silvestrii from western North America. The Eastern lineage includes the genus Aituaria and is the sister group of the Asian genera Nesticella and Wraios. The Domitius lineage is likely the sister group of the Central European lineage and spreads over the Iberian and Italian peninsulas. Finally, the Central European lineage includes three genera: Kryptonesticus, distributed from the karstic massifs of the Balkan Peninsula to Turkey, Nesticus with a single synanthropic species N. cellulanus and Carpathonesticus, exclusive to the Carpathian Mountains. With the exception of the genus Typhlonesticus, all European genera show an allopatric distribution (except for the two European synanthropic species). The results obtained in this study together with the revision of the original descriptions, redescriptions, and illustrations, lead us to propose 11 nomenclatural changes (new combinations) concerning the genera Typhlonesticus, Nesticus and Carpathonesticus.

New species of Plesiosorex (Eulipotyphla) from the middle Miocene of Gansu: the first record of Plesiosoricidae in China

ABSTRACT The new species Plesiosorex shanqini from the middle Miocene Galijia site in Linxia, Gansu Province, represents the first record of the Eulipotyphlan family Plesiosoricidae in China. Morphological characteristics show that P. shanqini has attained a moderate evolutionary level and shared features shown in European and North American taxa. This study supports that Plesiosorex originated in Eurasia and dispersed to North America in the early Miocene. In addition, it is speculated that this genus preferred to the predominance of a relatively arid shrub-steppe environment and adapted to a biotope preference dominated by open grasslands and with patches of bush or forests. urn: lsid:zoobank.org:pub:72739426-BE81-4967-A871-A30EC37E4951

New material of Incadelphys antiquus (Pucadelphyda, Metatheria, Mammalia) from the early Palaeocene of Bolivia reveals phylogenetic affinities with enigmatic North and South American metatherians

The present paper describes a partial skull referred to Incadelphys antiquus, from the early Palaeocene of Tiupampa (Bolivia). The specimen includes the anterior part of the skull with maxillae, premaxillae, nasals, lacrimals, anterior part of frontals and jugal, and both dentaries. Most of the teeth are preserved except some incisors. Some of the major characteristics of Incadelphys are the elongation and slenderness of the rostrum as compared to other Tiupampa taxa and the narrowness and blade-like morphology of the premolars. The new specimen is compared to the other Tiupampan pucadelphydans, especially, pucadelphyids, but also sparassodonts. Comparisons with Marmosopsis juradoi, from the early Eocene of Itaboraí and with Aenigmadelphys archeri from the latest Campanian of North America is also meaningful. Among others, the three genera share a strong distolabial extension of their metastylar area of the M1, which has not been observed, to a such extant, in other American metatherians. A phylogenetic parsimony analysis has been performed with exclusion some poorly known taxa, such as Jaskhadelphys minutus (two upper molars only), from Tiupampa or Kiruwamaq chisu (one M?3 only) from the late Eocene of Peru. The taxa included in our analysis are at least known from all upper and lower molars. The result of our analysis with unweighted characters retrieved the inclusion of Incadelphys, Marmosopsis, Szalinia and Aenigmadelphys in the clade Pucadelphyda, which also includes the Pucadelphyidae and the Sparassodonta. An analysis with downweighted homoplastic characters (with Goloboff K=3) resulted in a monophyletic grouping of Szalinia, Aenigmadelphys, Marmosopsis, and Incadelphys in an unnamed clade designated with the working term SAMI (after the initial of these four genera). This result, which we favor, is the first hypothesis which suggests a close relationship between the early Palaeocene - early Eocene, Tiupampa -Itaboraí pucadelphydans and a Late Cretaceous North American taxon, Aenigmadelphys, which is included within the Pucadelphyda.

Systematic revision of the Roseinae clade of Russula, with a focus on eastern North American taxa

ABSTRACT The Roseinae clade is a lineage of the genus Russula primarily composed of species of Russula subsect. Roseinae. Species in this morphologically distinct clade possess a white to pale cream spore print, mild taste, positive reaction to sulfovanillin, and primordial hyphae with acid-resistant crystals in the pileipellis. Here, we present a morphological and phylogenetic assessment that distinguishes seven eastern North American species of the core Roseinae lineage and a new subsection, Russula subsection Albidinae, to accommodate members of the Albida clade. We assign the previously described species R. peckii, R. rubellipes, and R. pseudopeckii to three species-level clades, and three other species, R. cardinalis, R. cordata, and R. rheubarbarina, are described as new. Comparative morphological analyses reveal differences in the conformation of terminal elements in the pileipellis, spore size, hymenial cystidia contents, and pigmentation on the stipe surface as key features to recognize species in the group. Based on the analysis of publicly available data, we recognize a potential total of nine temperate North American species within R. subsect. Roseinae, in addition to four from Central America, two from Europe, and 14 from Asia.

96 North American taxa sorted – Peck’s Hebeloma revisited

ABSTRACT Charles Horton Peck described some 2700 species of North American fungi in the 19th and early 20th centuries. Among these were 31 species that he described as Hebeloma or that later authors recombined into Hebeloma. These 31 taxa have been analyzed morphologically and molecularly, as far as possible. For six of these species, lectotypes are designated. For twelve species, ITS sequences (some partial) were generated. Thirteen of the species analyzed are Hebeloma, as the genus is delimited today. Of these 13, nine are regarded as ‘current’, i.e. are names that should be accepted and used. Of the remaining four, three are synonymized with earlier Peck species and one with the generic type H. mesophaeum. Numerous Hebeloma species described from America are synonymized with some of Peck’s species, such as H. albidulum, H. album, H. colvinii, H. excedens, H. palustre, H. sordidulum, and H. velatum; Peck’s H. album, H. palustre, and H. velatum are earlier names for H. fragilipes, H. clavulipes, and H. dunense, respectively. All three names were in current use and described from Europe. The 18 species that are not Hebeloma belong to a range of genera: Agrocybe, Hemistropharia, Inocybe, Inosperma, Naucoria, and Pholiota; three species that were not previously recombined into their respective genera are here recombined and one species, Hebeloma commune is synonymized with Pholiota lenta. Two taxa, that are not Hebeloma, remain unresolved. Sixty later Hebeloma taxa described from North America are revised and synonymized with Peck species and seven with H. mesophaeum, 36 of these supported by ITS (some partial) sequence data. Updates on two species, H. petrakii and H. remyi, from Europe, are also given, and a lectotype and epitype selected for the latter.

Molecular taxonomy and description of a new species of Limnodrilus (Naididae, Clitellata, Annelida) in China.

The freshwater annelid worm genus Limnodrilus, including the widely distributed L. claparedianus Ratzel, 1868, is common in Chinese freshwater ecosystems. One species, previously recognized as morphologically intermediate between L. claparedianus and the North American taxon L. cervix Brinkhurst, 1963, is here described as a new species, L. paraclaparedianus Zhou Cui n. sp., using both molecular and traditional taxonomy. Comparisons of sequences of the Cytochrome Oxidase subunit I (COI) mtDNA in a sample of Limnodrilus species showed that the distances between species were generally higher than the divergences within them. Phylogenetic analysis of COI as well as 16S mtDNA and Internal Transcribed Spacer 2 (ITS2) nDNA confirmed that the new species is an independent lineage. Moreover, morphological differences in the prostomium, characteristics of the chaetae and internal genitalia support the separation of the species.

Phylogenetic reappraisal and epitypification of Laccaria macrocystidiata (Hydnangiaceae, Basidiomycota)

Laccaria macrocystidiata, a marasmioid species, originally described as Laccaria affinis f. macrocystidiata from Central Italy, was synonymised with the North American taxon Laccaria laccata var. pallidifolia, but only on a morphological basis. In this paper, the independent position of L. macrocystidiata from L. laccata var. pallidifolia and other species of Laccaria is pointed out on the basis of ITS-LSU phylogenetic analyses. According to our results, Laccaria macrocystidiata var. longispinosa is considered a synonym of Laccaria macrocystidiata. Laccaria macrocystidiata holotype consists of only one basidioma in poor condition; thus, a new epitype from an Italian collection was designated.

Typifications and taxonomical rearrangements in North and Central American Tagetes (Asteraceae, Tageteae)

During the revision of the genus Tagetes, we detected the need for typifications and taxonomical rearrangements in North and Central American taxa. We analyzed type and non-type specimens, morphological traits, geographical distributions, protologues, and biographies of authors and collectors. As a result, we designated 12 lectotypes and one epitype for the following plant names: T. clandestina, T. florida, T. lemmonii, T. lucida, T. macroglossa, T. micrantha, T. nelsonii, T. oligocephala, T. schiedeana, T. signata, T. signata var. pumila and T. triradiata. In addition, we placed T. oligocephala in synonymy within T. foetidissima and clarified type localities of T. oligocephala and T. schiedeana.

Transcriptional profile of oil palm pathogen, Ganoderma boninense, reveals activation of lignin degradation machinery and possible evasion of host immune response

BackgroundThe white-rot fungi in the genus Ganoderma interact with both living and dead angiosperm tree hosts. Two Ganoderma species, a North American taxon, G. zonatum and an Asian taxon, G. boninense, have primarily been found associated with live palm hosts. During the host plant colonization process, a massive transcriptional reorganization helps the fungus evade the host immune response and utilize plant cell wall polysaccharides.ResultsA publicly available transcriptome of G. boninense - oil palm interaction was surveyed to profile transcripts that were differentially expressed in planta. Ten percent of the G. boninense transcript loci had altered expression as it colonized oil palm plants one-month post inoculation. Carbohydrate active enzymes (CAZymes), particularly those with a role in lignin degradation, and auxiliary enzymes that facilitate lignin modification, like cytochrome P450s and haloacid dehalogenases, were up-regulated in planta. Several lineage specific proteins and secreted proteins that lack known functional domains were also up-regulated in planta, but their role in the interaction could not be established. A slowdown in G. boninense respiration during the interaction can be inferred from the down-regulation of proteins involved in electron transport chain and mitochondrial biogenesis. Additionally, pathogenicity related genes and chitin degradation machinery were down-regulated during the interaction indicating G. boninense may be evading detection by the host immune system.ConclusionsThis analysis offers an overview of the dynamic processes at play in G. boninense - oil palm interaction and provides a framework to investigate biology of Ganoderma fungi across plantations and landscape.

Early Cretaceous charophytes from south Dobrogea (Romania). Biostratigraphy and palaeobiogeography

Eleven boreholes and one outcrop of the Lower Cretaceous in South Dobrogea (south-eastern Romania) were sampled for charophytes. Twenty species are described and illustrated in two non-marine rock units, the Zăvoaia Member and the Gherghina Formation. The Zăvoaia Member contains a charophyte assemblage dominated by Feistiella bijuescensis, aff. Mesochara harrisii, Nodosoclavator bradleyi, Clavator bilateralis, and Clavator grovesii var. grovesii, indicating a Berriasian age. Other less abundant species include Feistiella sp., Latochara sp., Mesochara dobrogeica sp. nov., Globator maillardii var. nurrensis, Atopochara trivolvis var. micrandra, Clavator grovesii var. discordis, Hemiclavator adnatus, and Hemiclavator neimongolensis var. posticecaptus. The occurrence of G. maillardii var. nurrensis in this assemblage suggests late Berriasian age. The Gherghina Formation is dominated by the species Atopochara trivolvis var. triquetra and Clavator grovesii var. jiuquanensis. Other less abundant species include Sphaerochara andersonii, aff. Mesochara harrisii, Globator maillardii var. trochiliscoides, Globator maillardii var. biutricularis, Clavator harrisii var. reyi, and Clavator ampullaceus var. latibracteatus var. nov. This assemblage indicates a late Barremian–early Aptian age. This study sheds new light on the palaeobiogeographical distribution of Lower Cretaceous charophytes in the Tethyan realm. Well-known western European charophyte species such as F. bijuescensis, S. andersonii, G. maillardii var. trochiliscoides, H. adnatus, and H. neimongolensis var. posticecaptus are herein described for the first time in eastern Europe. Very significantly, this is the first report in Europe of the hitherto North American taxon C. bilateralis, while the species C. ampullaceus has previously been reported only from the Middle East and eastern Africa.

<strong>New combinations in <em>Potentilla</em> for taxa originally validated or treated in <em>Ivesia</em>, <em>Horkelia</em>, and <em>Horkeliella</em> (Rosaceae: Potentilleae)</strong>

Nineteen new combinations (eight species-rank and 11 variety-rank ones) in Potentilla (Rosaceae, Potentilleae) are proposed for North American taxa that were originally validated or treated in Ivesia, Horkelia, and Horkeliella. These combinations are needed for those researchers and users of botanical nomenclature who prefer to subsume these taxa in Potentilla in its updated monophyletic (holophyletic) circumscription. That circumscription is mainly based on recent molecular phylogenetic results that demonstrated that the three ivesioid genera form a monophyletic lineage (ivesioid clade) that is phylogenetically rooted in the core clade of Potentilla. Nomenclatural comments are provided, and the rationale of those preferring the continued recognition of Ivesia, Horkelia, and Horkeliella is explained.

Pluteus dianae and P. punctatus resurrected, with first records from eastern and northern Europe

The type specimens of Pluteus dianae and P. punctatus from the Czech Republic were studied morphologically and molecularly. New collections identified by nrITS sequence analyses extend the distribution of P. dianae to Denmark, European Russia, and the Asian part of Turkey and of P. punctatus to Sweden. The application of these names is discussed; both belong in the P. plautus complex, and data on European and North American taxa in this complex are summarised and compared with P. dianae and P. punctatus. Pluteus aestivus is considered a nomen dubium.

A chromosome-scale reference genome of Aquilegia oxysepala var. kansuensis

The genus Aquilegia (Ranunculaceae) has been cultivated as ornamental and medicinal plants for centuries. With petal spurs of strikingly diverse size and shape, Aquilegia has also been recognized as an excellent system for evolutionary studies. Pollinator‐mediated selection for longer spurs is believed to have shaped the evolution of this genus, especially the North American taxa. Recently, however, an opposite evolutionary trend was reported in an Asian lineage, where multiple origins of mini- or even nonspurred morphs have occurred. Interesting as it is, the lack of genomic resources has limited our ability to decipher the molecular and evolutionary mechanisms underlying spur reduction in this special lineage. Using long-read sequencing (PacBio Sequel), in combination with optical maps (BioNano DLS) and Hi–C, we assembled a high-quality reference genome of A. oxysepala var. kansuensis, a sister species to the nonspurred taxon. The final assembly is approximately 293.2 Mb, 94.6% (277.4 Mb) of which has been anchored to 7 pseudochromosomes. A total of 25,571 protein-coding genes were predicted, with 97.2% being functionally annotated. When comparing this genome with that of A. coerulea, we detected a large rearrangement between Chr1 and Chr4, which might have caused the Chr4 of A. oxysepala var. kansuensis to partly deviate from the “decaying” path that was taken before the split of Aquilegia and Semiaquilegia. This high-quality reference genome is fundamental to further investigations on the development and evolution of petal spurs and provides a strong foundation for the breeding of new horticultural Aquilegia cultivars.

Re-examining ratio based premaxillary and maxillary characters in Eudromaeosauria (Dinosauria: Theropoda): Divergent trends in snout morphology between Asian and North American taxa

The clade Eudromaeosauria predominantly comprises medium to large Late Cretaceous Laurasian dromaeosaurids. Because many specimens are fragmentary, the maxilla has frequently been used to infer the proportions of the entire snout. Given the strong relationship between snout shape and feeding behaviour, such inferences have potentially important palaeobiological implications, but they should ideally be justified by explicit analysis. Maxillae have also been hypothesized to have high interspecific variability and are used to erect new taxa. However, many maxillary characters are based on proportions that may vary ontogenetically, sexually, and randomly within species, as well as phylogenetically. Proportionate characters are often unjustifiably coded in terms of discrete states even when they represent a continuum of variation.In this study, eudromaeosaurian maxillae were examined using bivariate (least squares regression) and multivariate (Principal Component Analysis and cluster analysis) methods, to discern the extent to which this skull element can be used to draw ecological and phylogenetic inferences. The length/height ratio of the maxilla was found to be a strong predictor of that of the premaxilla, justifying inferences about snout morphology from the former element alone. PCA and cluster analysis show a strong morphological dichotomy between Asian and North American taxa, and consistently recover congeneric specimens as being most alike. Maxillary characters from previous analyses were found to be divisible into discrete states, but to nevertheless illustrate the potential problems of using such characters in large datasets. Parsimony analysis of the revised premaxillary and maxillary characters resulted in a different tree topology than the most recent phylogenetic analyses, emphasizing the importance of this element in dromaeosaurid phylogenetics. Evolution of divergent snout morphologies in Asian and North American eudromaeosaurians may have been driven by selective pressures resulting from differences in the range of available prey, or in environmental variables such as aridity, between the two continents.

Revision of leccinoid fungi, with emphasis on North American taxa, based on molecular and morphological data

ABSTRACT The leccinoid fungi are boletes and related sequestrate mushrooms (Boletaceae, Basidiomycota) that have traditionally been placed in Leccinum, Boletus, Leccinellum, and a handful of other less familiar genera. These mushrooms generally feature scabers or scaber-like dots on the surface of the stipe, and they are often fairly tall and slender when compared with other boletes. They are ectomycorrhizal fungi and appear to be fairly strictly associated with specific trees or groups of related trees. In the present study, we investigate the phylogenetic relationships among the leccinoid fungi and other members of the family Boletaceae using portions of three loci from nuc 28S rDNA (28S), translation elongation factor 1-α (TEF1), and the RNA polymerase II second-largest subunit (RPB2). Two DNA data sets (combined 28S-TEF1 and 28S-TEF1-RPB2), comprising sequences from nearly 270 voucher specimens, were evaluated using two different phylogenetic analyses (maximum likelihood and Bayesian inference). Five major clades were obtained, and leccinoid fungi appeared in four of them. Taxonomic proposals supported by our results, representing a broadly circumscribed Leccinum that includes several sequestrate genera, along with Leccinellum, are made.

Neogene crocodylians from the Central Great Plains: spatiotemporal histories and relationships with regional climatic and environmental changes

ABSTRACT Crocodylian fossils are well documented from Upper Cretaceous and lower to middle Paleogene deposits in the mid-high latitudes of the Western Interior, whereas the only extant North American taxon, Alligator mississippiensis, is restricted to the lower-latitude wetlands of the southeastern United States. The departure of crocodylians from the Western Interior has been inferred to represent a major shift from more equable, warmer, wetter climates in the Paleogene to more seasonal, cooler, drier climates in the Neogene. The timing of further geographic range shifts during the Neogene, including the local extinction (extirpation) of crocodylians from the Great Plains, is poorly constrained. We document the Neogene crocodylian fossil record of the Central Great Plains (CGP) in order to constrain the timing of mid-continental crocodylian extinctions against a backdrop of climatic and environmental changes. The Neogene CGP crocodylian fossil record consists of mostly incomplete specimens, likely referable to the extant genus Alligator, and appears to document multiple latitudinal range shifts that are spatiotemporally consistent with regional climatic and environmental changes inferred from independent proxy evidence. The last appearance datum (LAD) for crocodylians in the CGP is ∼6 Ma, which suggests that climatic and environmental conditions in the region were unfavorable to crocodylians after this time. In general, Neogene crocodylian fossils throughout the Great Plains are not abundant. Barring taphonomic biases or sampling issues, this could imply low population densities, and/or that the fossil-bearing areas in this region were close to the northernmost limits of crocodylian (cf. Alligator) distributions during the Neogene.

Broad geographic sampling and DNA barcoding do not support thepresence of Helobdella stagnalis (Linnaeus, 1758) (Clitellata: Glossiphoniidae) in North America.

The description of Helobdella stagnalis (Linnaeus, 1758) has emphasized the presence of a nuchal, chitinous scute located on the dorsal surface in the first third of the body as the diagnostic character for the species. Historically, identifications of species of Helobdella have relied heavily on this character and, as a result, Helobdella stagnalis has been reported from an inordinately broad geographic range, including Europe, Asia, Africa, North America, and South America. In addition to a few earlier investigations, a recent analysis showed that great genetic distances (orders of magnitude greater than previous estimations of intraspecific divergence in leeches) are present between scute-bearing specimens identified as H. stagnalis from Europe and North America, implying that H. stagnalis does not occur in North America. The present study expands the geographic boundaries of taxon sampling for both European and North American taxa, and re-examines the phylogenetic relationships and cytochrome c oxidase subunit I (COI) variation within scute-bearing species of the genus Helobdella. Our analyses include specimens putatively identified as "Helobdella stagnalis" from Sweden, Norway, Iceland, England, France, Italy, Slovenia, Turkey, Russia, and Iran, as well as numerous localities covering Canada and the USA. Our results corroborate previous studies in that European and west Asian specimens form a clade, including the neotype, which is separate from North American taxa. To alleviate future taxonomic confusion, we redescribe H. stagnalis and designate a neotype from the inferred type locality. The designation of a neotype stabilizes the taxonomy of scute-bearing leeches of the genus Helobdella and enables us to definitively correct erroneous identifications reported in previous studies. We also note that at least four lineages of scute-bearing, North American species of Helobdella lack formal descriptions.