Platyarthridae

Distinguished from Trachelipodidae and other woodlice families by the absence of pleopodal lungs. Small size (<6 mm), very small eyes with <10 ommatidia, and inability to conglobate are key field characteristics. Within the family, Trichorhina species are identified by combinations of integument texture (granulate vs. smooth), arrangement of scale-setae, noduli laterales position, pereonite corner shape, pleon retraction, telson shape, and male pleopod I morphology. Molecular data (COI sequences) increasingly used for species delimitation, particularly for cryptic cave-dwelling forms.

Small woodlice, mostly less than 6 mm in length. Body dorsoventrally flattened, unable to roll into a ball (non-conglobating). Compound eyes very small, with fewer than 10 ommatidia. No pleopodal lungs present. Integument texture variable: some species with granulations arranged in longitudinal lines, others with smooth dorsal surfaces. Scale-setae often present, sometimes arranged in longitudinal lines. Noduli laterales (lateral sensory organs) present, with positions varying among species. Cephalon (head) typically not inserted into pereon (thorax). Pereonites with posterior corners ranging from convex to weakly sinuous. Pleon (abdomen) not retracted in relation to pereon. Telson shape variable: triangular with obtuse or rounded tip, or sub-triangular with widely rounded posterior edge. Neopleura (lateral pleonal extensions) may be large and falciform in some species.

Predominantly tropical habitats, with many species restricted to subterranean environments. Cave-dwelling species documented in limestone karst systems, iron ore caves, and groundwater calcretes. Surface-dwelling species occur in tropical forest litter and soil. Brazilian records include Atlantic Forest caves, Alto Ribeira karst area, and iron ore cave systems in the Amazon (Serra dos Carajás, Serra Leste, Serra da Bocaina, Serra do Tarzan, Serra Norte, Serra Sul). Ibero-Balearic populations occur in epigean (surface) habitats.

Primarily tropical distribution. Documented from: Brazil (Bahia, Mato Grosso, Mato Grosso do Sul, Minas Gerais, Pará, São Paulo states), Amazon region iron ore cave systems, Iberian Peninsula and Balearic Islands (Spain, Portugal), Western Australia (Yilgarn region), Queensland (Australia), and various tropical regions globally. Scandinavian records (Denmark, Norway, Sweden) present in GBIF but may represent introductions or misidentifications requiring verification.

Cave-dwelling behavior documented in numerous species, particularly in the genus Trichorhina. Subterranean populations show troglomorphic traits including reduced eyes and elongated appendages in some lineages. No conglobation behavior—members cannot roll into defensive balls.

• TrachelipodidaeSimilar body form and size, but distinguished by presence of pleopodal lungs (often inconspicuous) versus complete absence in Platyarthridae
• ParaplatyarthridaeFormerly confused with Platyarthridae; now recognized as distinct family based on morphological and molecular evidence. Australian species previously assigned to Trichorhina (Platyarthridae) reassigned to Paraplatyarthrus (Paraplatyarthridae)

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Everything is similar, everything is different! Trichorhina (Oniscidea, Platyarthridae) from Brazilian caves, with descriptions of 11 new species
• The genus Trichorhina Budde-Lund, 1908 (Crustacea, Isopoda, Platyarthridae) in the Ibero-Balearic region, with descriptions of three new species
• Investigating Patterns in New Species of Trichorhina Budde-Lund, 1908 Species (Isopoda: Platyarthridae) from Iron Ore Amazon Caves: Taxonomy and Insights into Their Ecomorphology
• Taxonomy of Paraplatyarthrus Javidkar and King (Isopoda: Oniscidea: <br />Paraplatyarthridae) with description of five new species from Western Australia, and comments on Australian Trichorhina Budde-Lunde, 1908 (Platyarthridae)