Taxonomic Consequences Research Articles

Diatoms as dandelions: convergent evolution in the reproductive biology of small Nitzschia species (Bacillariophyta) and its possible taxonomic consequences

ABSTRACT Nitzschia soratensis and N. inconspicua are two small diatoms that are extremely similar in the light microscope though separable in subtle aspects of valve and girdle ultrastructure. They are not closely related in molecular phylogenies and differ in their ecological preferences, though they sometimes co-occur in the same communities. To test further their functional equivalence, we investigated the reproductive biology of N. soratensis, for comparison with a previously published account of N. inconspicua. Both species are automictic, lacking pairing between gametangia and gamete exchange. Nuclear staining shows the presence of two nuclei in some auxospores of N. soratensis, which are smaller than the nuclei of vegetative cells and appear to be haploid, indicating prior meiosis. These auxospores, surrounded by incunabula containing tangles of silica strips, give rise to uninucleate initial cells 18–21 µm long. Frequently, however, small N. soratensis cells produce two spherical ‘pseudogametes’, some of which abort while others expand and form initial valves shorter than those produced by binucleate auxospores (maximum length 14.5 µm). Similar uniparental auxosporulation, with silica strip formation, occurs in N. aff. hantzschiana, N. acidoclinata, N. fonticola and N. angustata, which are close relatives of N. soratensis according to morphological and/or molecular evidence. This group and the N. inconspicua complex may be the diatom equivalents of apomictic angiosperms, e.g. dandelions, and likely contain a multitude of microspecies.

Phylogenetic analysis of museum specimens of houting Coregonus oxyrinchus shows the need for a revision of its extinct status

According to the IUCN Red List the anadromous houting Coregonus oxyrinchus is categorized as ‘extinct’. However, this extinct status might be incorrect because taxonomic difference between C. oxyrinchus and the closely related C. lavaretus is based on a disputable morphological comparison. Also, phylogenetic studies on mtDNA only focused on recent obtained coregonids. We are the first to perform a mtDNA analysis on both historic and recent specimens, including the syntype specimen which was used for species description by Linnaeus originally. Two primer pairs for mitochondrial CytB and ND3 were used to extract sequences for phylogenetic analysis. Sequences from 14 out of 21 C. oxyrinchus museum specimens were successfully obtained and compared with sequences from recent obtained C. lavaretus. The sequences were combined with GenBank data from a previous phylogenetic study on houting to create a phylogenetic tree and two minimum spanning haplotype networks. Results show that C. oxyrinchus and C. lavaretus form a clade with limited genetic variation. Low bootstrap values also show weak support for geographical patterns in distribution of mitochondrial haplotypes. Statistical analysis of the haplotype networks also shows that historic and recent specimens are similar species. Our results suggest that C. oxyrinchus is a junior synonym of C. lavaretus. A definitive taxonomic revision could not be made because only CytB sequencing was successful for the syntype specimen. We discuss taxonomic consequences and the species-specific focus in nature conservation. We propose a shift in nature conservation to a more functional approach based on traits rather than species.

Phylogeny and infrageneric classification of Clerodendrum (Lamiaceae)

Abstract The infrageneric classification of the genus Clerodendrum (Lamiaceae) has been highly problematic due to different concepts and subdivisions being applied to the treatment of Asian, Australian, and African species. Earlier molecular phylogenetic studies based on Sanger sequencing and limited sampling have indicated that previous morphology-based infrageneric classifications are not congruent with the phylogeny due to morphological convergence in many lineages. Advances in high-throughput DNA sequencing provide more information allowing more robust phylogenetic reconstruction at larger scale. We present the first comprehensive phylogenetic study of Clerodendrum that includes representatives of all previously recognized infrageneric taxa and using targeted sequencing data obtained from the Angiosperms353 enrichment to resolve the phylogenetic relationships. In agreement with previous phylogenetic work, our phylogeny shows that Asian and Australian species form a sister clade to an African Clade. Clerodendrum is monophyletic with the exclusion of some tropical coastal species, including some Australian species, which fall within a clade containing Volkameria and New World genera. We recognize two subgenera: subgen. Clerodendrum for Asian and Australian species and the new subgen. Afroclerodendrum for African and Malagasy species. Our findings support an infrageneric classification of Clerodendrum with a total of 13 sections based on molecular phylogenetic evidence and morphology that clearly accommodate the Asian, remaining Australian, and African species. Of these, we propose three new sections: sect. Albiflora, sect. Fortunata and sect. Megaflora for clades presenting unique morphological characters. The sectional classification and taxonomic consequences are discussed.

Note on genitalia and taxonomy of the Callidiopini from the Philippines, with description of six new species and two subspecies (Coleoptera, Cerambycidae, Cerambycinae)

Species of Ceresium and Examnes, Callidiopini, from the Philippines were reviewed. Six new species, Ceresium elongatipennesp. nov., Ceresium holzschuhisp. nov., Ceresium jimcopeisp. nov., Ceresium nigricollesp. nov., Ceresium quinquemaculatumsp. nov., Ceresium crassumsp. nov. and one new subspecies, Ceresium huedepohli mindanaosubsp. nov., are described. Of Examnes, one new subspecies, Examnes lumawigi subrugosussubsp. nov., is described. Male genitalia of eight Ceresium species and three Examnes species, in particular their endophalli and 8th sternites, are described and illustrated in detail. Female genitalia of three Ceresium species are described. The genitalia and the consequences for taxonomy are discussed.

Characterisation of a Spontaneous Mutant of Lemna gibba G3 (Lemnaceae).

A spontaneous mutant of the duckweed Lemna gibba clone no. 7796 (known as strain G3, WT) was discovered. In this mutant clone, L. gibba clone no. 9602 (mt), the morphological parameters (frond length, frond width, root length, root diameter) indicated an enlarged size. A change in the frond shape was indicated by the decreased frond length/width ratio, which could have taxonomic consequences. Several different cell types in both the frond and the root were also enlarged. Flow cytometric measurements disclosed the genome size of the WT as 557 Mbp/1C and that of the mt strain as 1153 Mbp/1C. This represents the results of polyploidisation of a diploid clone to a tetraploid one. The mutant clone flowered under the influence of long day-treatment in half-strength Hutner's medium in striking contrast to the diploid WT. Low concentration of salicylic acid (<1 µM) induced flowering in the tetraploid mutant but not in the diploid plants. The transcript levels of nuclear-encoded genes of the photosynthetic apparatus (CAB, RBCS) showed higher abundance in light and less dramatic decline in darkness in the mt than in WT, while this was not the case with plastid-encoded genes (RBCL, PSAA, PSBA, PSBC).

ROWANS, WHITEBEAMS AND SERVICE TREES

ROWANS, WHITEBEAMS AND SERVICE TREES

Critical comments on the article by Wang et al. "Lectotypification of the name Brachyscome neocaledonica = Pytinicarpa neocaledonica (Asteraceae: Astereae)" published in the Ukrainian Botanical Journal (2022, 79(2): 77–83)

In this note, we highlight a series of possible misinterpretations (collectors, localities, previous writings) and other problems in the nomenclatural study by Wang et al. (2022) on lectotypification of the name Brachyscome neocaledonica ≡ Pytinicarpa neocaledonica (Asteraceae: Astereae). In our opinion, this lectotype designation led to debatable conclusions that added confusion to taxonomy of Pytinicarpa G.L.Nesom, an already taxonomically complicated genus. However, we accept that type designation and explain its nomenclatural and taxonomic consequences.

Morphological, Morphometrical and Molecular Characterization of Oscheius siddiqii Tabassum and Shahina, 2010 (Rhabditida, Rhabditidae) from India with Its Taxonomic Consequences for the Subgenus Oscheius Andrássy, 1976.

Simple SummaryDue to their potential entomopathogenicity, nematodes of the genus Oscheius have been in the spotlight of the scientific interest in recent years. Unfortunately, some of these species are poorly described and have inadequate or no molecular support. This fact complicates the systematics of the group, and a revision of these species is necessary to elucidate their taxonomic status. In the present study, we provide a detailed description based on the morphological, morphometrical, and molecular characteristics of Oscheius siddiqii from Uttar Pradesh, India, including the first scanning electron microscopy (SEM) studies of the species. Furthermore, based on morphological and molecular data, the status of some Oscheius species is discussed, and several synonymisations are proposed.An insect parasitic nematode belonging to the genus Oscheius was recovered from the agricultural soils from the Hapur district in western Uttar Pradesh, India. Morphological studies on this species exhibited its high resemblance with two Pakistani species: Oscheius siddiqii and O. niazii. No molecular data are available for these taxa but, morphologically, both species do not differ significantly from our strains and each other. Hence, these nematodes can be considered conspecific, and the correct name for this taxon is O. siddiqii, the first described species. The phylogenetic analyses of the ITS-, 18S-, and the 28S rDNA sequences showed that O. siddiqii is a sister taxon to the group formed by Oscheius microvilli, O. myriophilus, O. safricanus, and several unidentified Oscheius species. Additionally, our analyses show that based on molecular and morphological data, the species Oscheius rugaoensis and O. microvilli cannot be distinguished from O. chongmingensis and O. myriophilus, respectively, and are thus considered junior synonyms of these taxa. Furthermore, the available data are not sufficient to evaluate the status of Oscheius basothovii and O. safricanus, which are, in consequence, considered species inquirendae. These findings highlight the necessity of the proper morphological and molecular characterisation of the described Oscheius species.

Lectotypification of the Linnaean name Dianthus virgineus (Caryophyllaceae) and its taxonomic consequences

AbstractA lectotype is designated for the name Dianthus virgineus. The relationships between D. virgineus, D. caryophyllus var. caryophyllus, and D. caryophyllus var. inodorus are analyzed. Dianthus virgineus is the oldest available name that applies to a species complex that is often referred to as D. sylvestris or a broad circumscription of the cultivated ornamental D. caryophyllus. The taxonomic consequences are discussed, and the need for further studies is highlighted.

Apertochrysa Tjeder, 1966, a new senior synonym of Pseudomallada Tsukaguchi, 1995 (Neuroptera: Chrysopidae: Chrysopinae: Chrysopini).

Apertochrysa Tjeder, 1966, is identified as a new senior subjective synonym of the large, subcosmopolitan, green lacewing genus currently known under the name Pseudomallada Tsukaguchi, 1995. Apertochrysa is rediagnosed and the taxonomic consequences of the new synonymy are reviewed. New combinations are created in Apertochrysa for 165 species formerly placed in Pseudomallada and for two species formerly placed in Mallada; three species are transferred from Pseudomallada back to previously-established combinations in Apertochrysa; and 13 additional species are retained in Apertochrysa from previous placements. This brings the total number of Apertochrysa species to 183.

Quest for the type species of the genus Hepatozoon – phylogenetic position of hemogregarines of rats and consequences for taxonomy

The genus Hepatozoon is the most diversified and prevalent of all hemogregarine genera, which leads to a range of taxonomic challenges. Under-sampling and missing molecular data from rat-originating Hepatozoon muris, the type species of the genus Hepatozoon, complicated all efforts of systematic revision of individual subclades. To clarify the taxonomy of Hepatozoon at the genus level and to restrict the usage of this generic name to a particular clade of hemogregarines, we analysed 18S rDNA sequences of Hepatozoon from three species of rats from two isolated island populations. To assess the genetic variability, we analysed complete mitochondrial genome sequences of the two closely related isolates. Phylogenetic analyses revealed the position of both closely related Hepatozoon genotypes within the 18S rDNA clade including rodent/amphibian/reptile sequences, seriously challenging the validity of the previously proposed genus Bartazoon.

Redescription and synonymization of Oscheius citri Tabassum, Shahina, Nasira and Erum, 2016 (Rhabditida, Rhabditidae) from India and its taxonomical consequences - CORRIGENDUM.

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Redescription and synonymization of Oscheius citri Tabassum, Shahina, Nasira and Erum, 2016 (Rhabditida, Rhabditidae) from India and its taxonomical consequences.

A population of a nematode species belonging to the genus Oscheius was isolated in western Uttar Pradesh, India. Morphological and morphometrical studies on this species showed its high similarity with six species described previously from Pakistan (Oscheius citri, O. cobbi, O. cynodonti, O. esculentus, O. punctatus and O. sacchari). The molecular analysis of the ITS1-5.8S-ITS2 rDNA sequences of the Indian population and the six species described from Pakistan showed that all the sequences are almost identical. Thus, based on morphological and molecular characteristics, all of the six above-mentioned Pakistani species and Indian strain do not differ from each other, hence can be considered synonyms. The correct name for this taxon is the first described species O. citri. Additionally, the phylogenetic analysis of the 18S rDNA and the 28S rDNA sequences showed that Oscheius citri is sister to the clade formed by O. chongmingensis and O. rugaoensis from China. The high similarity of morphological and morphometric characteristics of O. citri and other species, O. maqbooli, O. nadarajani, O. niazii, O. shamimi and O. siddiqii, suggest their conspecificity; however, lack of molecular data for these species does not allow this hypothesis to be tested.

Molecular systematics of the tribe Prismatomerideae (Rubiaceae) and its taxonomic consequences, with notes on the importance of the inflorescence morphology for species‐group recognition in Rennellia

AbstractTropical Asia is one of the centers of species diversity of flowering plants, in particular the coffee family (Rubiaceae). Prismatomerideae (the Psychotrieae alliance, subfamily Rubioideae) are a mostly Southeast Asian tribe encompassing four genera of shrubs and small trees (monospecific Gentingia and Motleyia, Prismatomeris with 16 spp., Rennellia with 4–5 spp.). We conducted molecular phylogenetic analyses of this group based on the nuclear and plastid sequence data from six markers and using Bayesian inference. The main goal was to produce a robust phylogeny of the tribe, which was subsequently used to (1) reassess its monophyly and phylogenetic position within the Psychotrieae alliance; (2) rigorously test the monophyly of Prismatomeris and Rennellia; (3) assess the phylogenetic relationships between the genera; and (4) evaluate the phylogenetic value of the inflorescence type currently used for species recognition in Rennellia. Motleyia was not sequenced due to the lack of material, and therefore its affinity with the other genera was assessed based on morphology. The tribe was supported as monophyletic and resolved as sister to the (Gaertnereae (Mitchelleae‐Morindeae)) clade. The monophyly of Prismatomeris sensu Johansson was strongly supported, but we argue for the merging of the monospecific genus Motleyia into Prismatomeris based on their strong morphological similarities coupled with the paraphyly of Prismatomeris with respect to Motleyia. Rennellia was strongly supported as paraphyletic with respect to Gentingia. We propose the transfer of the monospecific genus Gentingia to Rennellia, also consistent with their strong morphological resemblance. Prismatomerideae were resolved in two major sister lineages, the Prismatomeris and Rennellia clades, corresponding to our broadly delimited Prismatomeris and Rennellia. Three well‐supported and morphologically distinct subclades were identified within Rennellia s.l., of which one was represented by Rennellia subsessilis, with sessile and reduced umbel‐like inflorescences bearing two to four flowers. The other two subclades have compound spike‐like (or sub‐raceme‐like) and raceme‐like inflorescences, an important distinction in species‐group recognition. We conclude that inflorescence type shows a strong phylogenetic signal and is, therefore, a reliable feature for recognizing groups of species in Rennellia. Additional taxonomic characters are, however, needed for teasing apart closely related species with the same inflorescence types. Subsequent to our taxonomic revision, the tribe Prismatomerideae comprises two genera: Prismatomeris and Rennellia. One and two new combinations, respectively, are presented, bringing the total number of species in the tribe to 25, of which 17 are in Prismatomeris and 8 in Rennellia. A new species key to Rennellia s.l. is presented.

First report of powdery mildew caused by Podosphaera xanthii on the invasive Verbena brasiliensis in Texas.

Brazilian verbena (Verbena brasiliensis, family Lamiaceae) is a highly invasive plant found throughout the southern portion of the United States. As suggested by its name, it originates in South America but has prospered in the US due to its highly ruderal growing pattern and its ability to tolerate drought and disturbance. During the summer of 2019, sixty-four V. brasiliensis plants were growing in the University of Houston's temperature-controlled greenhouse (Houston, TX). Eight plants exhibited symptoms of powdery mildew infection on the stems and adaxial surface of the leaves. White circular powdery colonies with high numbers of aerially dispersing spores were observed on leaves, seemingly uncorrelated with leaf age. Upon examination, chlorosis of leaf tissue was detected in areas of infection. Conidiophores (n=25) were on average 210 μm in length and produced 6 to 9 conidia in true chains. Base-cells of conidiophores branched from hyphae forming right angles and averaged 35 μm long at the base. Conidia were hyaline, ovate, and measured 28-31 × 19-21μm. These structures are typical of the powdery mildew oidium anamorph of the genus Podosphaera. No chasmothecia were observed within colonies.The morphological characteristics and measurements were consistent with those of Podosphaera xanthii (Braun and Takamatsu 2000). Pathogenicity was confirmed by gently rubbing symptomatic V. brasiliensis leaves onto healthy leaves of V. brasiliensis plants (Lee 2013). Fifteen plants were inoculated, and five remained uninoculated to serve as negative controls. Inoculated plants developed powdery mildew symptoms between 6 to 12 days (averaging 10 days), whereas all controls remained disease-free. DNA was extracted from fungal tissue from the original plant, inocula sample, and the newly infected leaves. The internal transcribed region was amplified using the ITS1f and ITS4 primers (White 1990). Three samples, one from the original plant, the inocula, and the reisolated fungi were sequenced, identified using NCBI BLAST, and the resulting sequences were deposited in GenBank (MN818562, (inocula), MN818563 (re-isolate), MN818564 (original)). All three sequences had 98.7% similarity to the P. xanthii on Brazilian verbena reported in South Korea assession number KJ472787 (Cho et al 2014). All three samples were amplified using the mating type primer sets and PCR protocal described in Brewer et al 2011. All three samples were determined to be MAT1-1-1 based on positive and negative control used for MAT1-1-1 and MAT-1-2-1 Positive controls included DNA from confirmed isolates from MAT1-1-1 and MAT-1-2-1 and negative controls were sterile water. Podosphaera xanthii, a common powdery mildew species, has been reported on a large range of important agricultural hosts, especially cucurbits (McCreight 2006). This is the first formal report of P. xanthii in Texas as well as the first report on Brazilian verbena in the United States. While we did not explicitly measure the pathogen's effect on host fitness, infection may result in a reduction in the plant's invasiveness. As Texas is a large producer of cucurbits, this pathogen could impact agriculture in the state. Given the invasive nature of V. brasiliensis in areas of high disturbance, such as agricultural fields and restored prairies, this discovery has broad importance for both agriculture and the ecological conservation of native species. Acknowledgments This work was supported by the National Science Foundation (Award #DEB-1754287), Texas Ecolab, and the University of Houston. References Braun, U., Takamatsu, S. 2000. Phylogeny of Erysiphe, Microsphaera, Uncinula (Erysipheae) and Cystotheca, Podosphaera, Sphaerotheca (Cystotheceae) inferred from rDNA ITS sequences-some taxonomic consequences. Schlechtendalia 4:1-33. Brewer, M. T., Cadle-Davidson, L., Cortesi, P., Spanu, P. D., and Milgroom, M. G. 2011. Identification and structure of the mating-type locus and development of PCR-based markers for mating type in powdery mildew fungi. Fungal Genet. Biol. 48:704-713. Cho, S. E., Park, J. H., Hong, S. H., Kim, B. S., & Shin, H. D. 2014. First report of powdery mildew caused by Podosphaera xanthii on Verbena brasiliensis in Korea. Plant Dis. 98:8, 1159. Lee, H. B. 2013. First report of powdery mildew caused by Podosphaera xanthii (syn. P. fusca)n cocklebur in Korea. Plant Dis. 97(6), 842. McCreight, J. D. 2006. Melon-powdery mildew interactions reveal variation in melon cultigens and Podosphaera xanthii races 1 and 2. Journal of the American Society for Horticultural Science, 131(1), 59-65.

Phenotypic masquerade: Polymorphism in the life cycle of the centrohelid heliozoan Raphidiophrys heterophryoidea (Haptista: Centroplasthelida)

The life cycle of the centrohelid heliozoan Raphidiophrys heterophryoidea Zlatogursky, 2012 was studied with light and electron microscopy in clonal cultures from the type locality. The alternation of two types of trophozoites, having contrastingly different morphology, was observed. Type 1 trophozoites morphology matched the original description. Type 2 trophozoites tended to form colonies usually of 6–8 individuals, connected with cytoplasmic bridges and their cell size was noticeably bigger, namely 43−45 μm compared to 24.5 μm on average in type 1 trophozoites. Some colonies were forming stalks composed of three or four axopodia covered with scales. Spicules were lacking completely, while plate-scales differed from those of type 1 trophozoites: they had oblong-elliptical shape, larger (5.9–14.1 × 2.4–5.8 μm) size, non-branching septa always reaching scale centre, solid upper plate. The conspecificity of the two trophozoite types was confirmed with the comparison of SSU rDNA gene sequence data. Both types of trophozoites were capable of encystment and excysted individuals always were type 1 trophozoites. A new type of cyst-scales (cup-scales) was described. Transitions between cysts and the two trophozoites types were documented. The diagnosis of R. heterophryoidea was improved accordingly. The possible functions, driving forces, and taxonomic consequences of the polymorphism were discussed.

Variations in palpal ornamentation of Anopheles fluviatilis species T and U (Diptera: Culicidae) and their taxonomic consequence

Anopheles fluviatilis sensu lato James is a highly efficient malaria vector in Indian subcontinent and Iran which is comprised of at least four sibling species provisionally designated as species S, T, U and V. An important morphological characteristic for differentiation of this species complex from other closely related anopheline species complex, the Minimus Complex, is the ratio of length of subapical pale band to dark band intervening apical and subapical pale bands on the maxillary palps of female mosquito. Here, we report variation in the subapical pale band in An. fluviatilis , especially in species U, to the extent that palps of some specimens resemble members of Minimus Complex, inferring that palpal ornamentation may not be reliable characteristics for identification of An. fluviatilis . Taxonomic consequence of such variation is discussed

Phylogenetic differentiation and taxonomic consequences in the Saurodactylus brosseti species complex (Squamata: Sphaerodactylidae), with description of four new species.

We divide Saurodactylus brosseti into five species, based on molecular and morphological characteristics. Phylogenetic analysis of two mitochondrial markers (ND4 and 12S rRNA) reveals five separately evolving lineages (clades) in the S. brosseti species complex. Each can be assigned to a particular geographical range within the distribution area in Morocco: North, South, Anti-Atlas, East and Southeast. A dichotomous key for all species within the genus Saurodactylus is presented. Despite the high level of color pattern variation among and within the northern, southern, Anti-Atlas and eastern clades, the southeastern lineage shows a unique coloration which is not found in other clades. The ecological traits of the southeastern clade seem to differ from those of the other four lineages since it is basically associated with Acacia species. Like the relictual ecosystem characterized by these trees, it appears to be highly threatened by extinction.

The morphometrics of autopolyploidy: insignificant differentiation among sexual-apomictic cytotypes.

Polyploidization of the plant genome affects the phenotype of individuals including their morphology, i.e. size and form. In autopolyploids, we expect mainly nucleotypic effects, from a number of monoploid genomes (i.e. chromosome sets) or genome size, seen from an increase in size or dimension of the polyploids compared with the diploids (or lower ploids). To identify nucleotypic effects, confounding effects of hybridity (observed in allopolyploids), postpolyploidization processes or environmental effects need to be considered. We morphometrically analysed five ploidy cytotypes of the sexual–apomictic species Potentilla puberula cultivated ex situ under the same experimental conditions. Sexuals are mainly tetraploid, while higher ploidy (penta- to octoploidy) is typically associated with the expression of apomixis. The cytotypes likely arose via autopolyploidization although historic involvement of another species in the origin of apomicts cannot be fully ruled out, suggested by a slight molecular differentiation among reproductive modes. We (i) revisited molecular differentiation using amplified fragment length polymorphisms and performed a morphometric analysis to test (ii) if cytotypes are morphologically differentiated from each other and (iii) if the size of individuals is related to their ploidy. Weak molecular differentiation of sexual versus apomictic individuals was confirmed. Cytotypes and reproductive modes were also morphologically poorly differentiated from each other, i.e. apomicts largely resampled the variation of the sexuals and did not exhibit a unique morphology. Overall size of individuals increased moderately but significantly with ploidy (ca. 14 % in the comparison of octo- with tetraploids). The results support an autopolyploid origin of the P. puberula apomicts and suggest a nucleotypic effect on overall plant size. We discuss taxonomic consequences of the results in the context of data on reproductive relationships among cytotypes and their ecological preferences and evolutionary origin, and conclude that cytotypes are best treated as intraspecific variants within a single species.

Fulfilling the taxonomic consequence after DNA Barcoding: Carychiumpanamaense sp. n. (Eupulmonata, Ellobioidea, Carychiidae) from Panama is described using computed tomographic (CT) imaging.

Five years ago, the Panamanian evolutionary lineage (EL) C12 was uncovered along with four other ELs in an integrative phylogenetic investigation of worldwide Carychiidae. Since EL C12 lacked shell material post-molecular analysis to serve as a museum voucher, it remained undescribed. Now, after recent collection efforts of C12 and the congener, Carychiumzarzaae Jochum & Weigand, 2017 at their original Panamanian sites, C12 is morphologically described and formally assigned the name, Carychiumpanamaense Jochum, sp. n. In sync with recent taxonomic treatment of the genus, computed tomography (CT) is used in this work to differentiate shells of C.panamaensesp. n. from geographically-proximal, Caribbean, North and Central American congeners. Recent material of topotypic Carychiumjardineanum (Chitty, 1853) and undamaged C.zarzaae were additionally CT-scanned and assessed in the comparative analyses.