Taxonomic Implications Research Articles

The largest ornithopod (Dinosauria: Ornithischia) from the Upper Jurassic of Europe sheds light on the evolutionary history of basal ankylopollexians

Abstract Ankylopollexia was an abundant and diverse clade of ornithopods present in North America, Europe, Africa, and Asia from the Late Jurassic to the Late Cretaceous. However, the relationships between the basal ankylopollexians are poorly understood. A new ankylopollexian ornithopod genus and species is described here, based on a dentary tooth, an ungual pollex of the manus, and an almost complete left hindlimb. The fossils come from deposits of the Villar del Arzobispo Formation (upper Kimmeridgian–Tithonian). Phylogenetic analysis revealed that Oblitosaurus bunnueli gen. et sp. nov. is the basalmost member of Ankylopollexia, together with Draconyx loureiroi. Furthermore, these results have relevant taxonomic implications for the genus Camptosaurus, being the first phylogenetic analysis to support the monophyly of Camptosaurus species. The estimated size of Oblitosaurus bunnueli suggests that it is the largest ornithopod described in the Upper Jurassic of Europe and one of the largest around the world, and could be the trackmaker of large ornithopod tracks found in the Upper Jurassic of the Iberian Peninsula. This discovery increases the known ankylopollexian diversity in Iberia, revealing the presence of an Iberian basal ankylopollexian clade that does not appear to be present in the contemporaneous outcrops of North America.

Karyotype diversity in four Terminalia L. species and its taxonomic implications

AbstractFour Terminalia L. species namely, T. arjuna (Roxb.) Wight and Arn., T. bellirica (Gaertn.) Roxb., T. chebula Retz. and T. catappa L. were studied to evaluate the chromosomal relationship corresponding with their taxonomic characters. Analysis of mitotic metaphases showed that the somatic chromosome numbers and the centromeric formulas of these species were 2n = 24 (16m + 8sm) for T. arjuna, 2n = 48 (36m + 12sm) for T. bellirica, 2n = 48 (46m + 2sm) for T. chebula and 2n = 24 (24m) for T. catappa. Two pairs of satellites were found in T. bellirica and T. catappa. Based on different karyological data, T. chebula was positioned in 1A, T. arjuna and T. catappa in 1B and T. bellirica in 2B. Based on comparative karyomorphological data, T. bellirica and T. arjuna presented more advanced features in comparison with T. chebula and T. catappa, which also correlated with the taxonomic characters in respect of the evolutionary point of view. Therefore, the present investigation effectively evaluated chromosomal relationships with morphological implications that conferred upon evolutionary changes among these four Terminalia species.

Morphological and taxonomic implications of the formation of colonies in Cyclostephanos and Stephanodiscus (Bacillariophyta)

ABSTRACT The importance of diatoms in bioindication and palaeolimnology is significant. For these applications, and species identification in general, a sound understanding of morphological variability is essential. Some species of the centric diatom genera Cyclostephanos and Stephanodiscus can form long, chain-like colonies. In these genera colony formation is associated with the morphology of the spines, which hold the cells together. One objective of this study was to investigate other possible differences in the valve morphology of solitary and colonial cultures. In addition, all strains were sequenced to account for the possibility that solitary and colonial forms may be different species, using three different loci (LSU, rbcL, cox1). The results show that colony formation not only affects the spine morphology but also other morphological features of the valve. The current interpretation that C. invisitatus and C. delicatus are facultative colony formers is supported by the results of this study. The evidence furthermore suggests that C. incognitus is a morphotype of C. invisitatus. A similar morphological pattern leads to the hypothesis that S. hantzschii and S. binderanus could possibly be solitary and colonial forms of the same species, which is also in agreement with the molecular analysis. These findings have implications for the taxonomy of the group and its application and open up a way for future investigations of morphological changes due to colony formation in other groups and taxa.

A revision and histological investigation of Saltoposuchus connectens (Archosauria: Crocodylomorpha) from the Norian (Late Triassic) of south-western Germany

Abstract Crocodylomorpha is the stem-lineage of modern crocodylians and the only pseudosuchian (i.e. crocodylian-line archosaurs) clade that survived the Triassic–Jurassic mass extinction event. Its earliest members, the non-crocodyliform crocodylomorphs, also known as ‘sphenosuchians’, were terrestrial and mostly small-bodied (<2 m long), although some large-bodied forms are known. Saltoposuchus connectens is one of the first described crocodylomorph species but it remains poorly studied, in part due to its contentious taxonomy. Here, all referred Saltoposuchus specimens are described in detail for the first time and its taxonomy is revised, with additional taxonomic implications for the British crocodylomorph Terrestrisuchus gracilis and the coelophysoid theropod Procompsognathus triassicus. Saltoposuchus connectens is clearly distinguished from Terrestrisuchus gracilis based on both cranial and postcranial features. The phylogenetic analysis finds that Saltoposuchus connectens, Terrestrisuchus gracilis, and Litargosuchus leptorhynchus form a clade of gracile, long-legged crocodylomorphs, identified as Saltoposuchidae Crush 1984. A histological section of a femur reveals highly vascularized fibrolamellar tissue in the second-largest specimen of Saltoposuchus connectens (SMNS 12596), indicating sustained high growth rates. A similar pattern was previously observed in Terrestrisuchus sp., contrasting with slower growth rates in the crocodylomorph Hesperosuchus agilis. These findings suggest that saltoposuchids had a high resting metabolic rate and active lifestyle.

Population Structure and Genetic Differentiation in Extant Alligator Snapping Turtles (genus Macrochelys) with Implications for Taxonomy and Conservation

Historically believed to harbor unrecognized diversity, the taxonomy of the declining genus Macrochelys (alligator snapping turtles) is debated. The original species, M. temminckii, was recently split into M. temminckii, M. apalachicolae, and M. suwanniensis. However, the status of M. apalachicolae is contested. In this study, we generated thousands of genome-wide loci to quantify population structure and genetic differentiation across the range of Macrochelys spp. Our data indicate that M. apalachicolae is genetically distinct, with little gene flow between M. apalachicolae and other species, thus adding evidence that M. apalachicolae may be a distinct species. We also find genetic variation partitioned among river drainages, with very high intra- and interspecific genetic divergence among river drainages. We suggest that translocations and re-introductions only move turtles in this genus within their natal river drainages to preserve existing patterns of genetic diversity.

Catfishes of the Genus Glyptothorax (Siluriformes: Sisoridae) in the Mae Klong River Basin, Thailand, with Taxonomic Implications for Several Southeast Asian Species

Catfishes of the Genus Glyptothorax (Siluriformes: Sisoridae) in the Mae Klong River Basin, Thailand, with Taxonomic Implications for Several Southeast Asian Species

Pollen morphology of family Thymelaeaceae Juss. in India and its taxonomic implications

We provide pollen morphology and ultrastructure of 26 plant taxa, comprising 14 genera, 21 species, 1 sub-species and 3 varieties, of the Thymelaeaceae family from the Indian sub-continent using light micsoscopic (LM) and scanning electron microscopic (SEM) techniques. The principal aim was to provide new and useful information regarding the extent of the pollen morphological diversity among the Thymelaeaceae taxa and, thus, contribute to a better understanding of the taxonomy of the studied taxa. The pollen grains of the studied taxa are essentially radially symmetrical, apolar, (released as) monad, pantoporate with a typical crotonoid pattern, and spheroidal (mostly) in shape; but widespread variations with respect to the number and dispensation of pores, size, exine (ectoexine and endoexine) thickness, and the shape itself (spheroidal, sub-spheroidal and prolate spheroidal), as well as in the amb (outline) have been also recorded. Pollen identification keys, based on the pollen micro-morphological attributes, were also constructed in order to easily identify the 26 studied Thymelaeceae taxa up to species and/or varieties level (high taxonomic resolution, showing taxonomic significance). The pollen morphological attributes of the 26 studied plant taxa of the Thymelaeaceae family were subjected to Principal Component Analysis (PCA) and Hierarchical Component Analysis (HCA), which suggest four clusters. The cophenetic correlation coefficient also validates the four group of clustering. The study will significantly help in the precise pollen identification in fossil (pollen) records for the reconstruction of vegetation dynamics and contemporary climate change during the Quaternary Period in India. Moreover, the present study also helps in determining the phylogenetic and evolutionary trend on the basis of the presence or absence of exine ornamentation and having more or less apertures among the pollen grains of the 26 studied Thymelaeaceae taxa.

Geography and past climate changes have shaped the evolution of a widespread lizard in arid Central Asia

The complex orogenic history and structure of Central Asia, coupled with Pleistocene glacial cycles have generated its stepwise aridification. Such events would have significantly influenced the evolution of many mid-latitude species in arid Central Asia (ACA). In this study, we employed two mitochondrial genes (CO1 and ND2) and genome-wide SNPs, coupled with ecological niche modeling, to investigate the lineage diversification and historical demography within a widespread lizard Phrynocephalus helioscopus, and their associations with geography and past climate change. We obtained the mtDNA dataset for 300 individuals from 96 localities within the known range of the lizard, among which 51 individuals from 27 localities were selected for generating the SNP dataset via the genotyping-by-sequencing approach. Phylogenetic analyses of the concatenated mtDNA dataset revealed eight geographically correlated lineages that diverged by 4.21–10.41% for the CO1 gene, which were estimated to have coalesced ∼4.47 million years ago. However, we observed mito-nuclear discordance pattern regarding the population of Clade V (P. helioscopus sergeevi) from Tajikistan. Ancestral area estimations suggested that P. helioscopus originated from the Fergana Valley and then dispersed into the adjacent areas in ACA along with a history of multiple allopatric divergence processes, suggesting that Fergana may have been the cradle of diversification of P. helioscopus. The intensification of aridification across Central Asia during the Late Pliocene may have facilitated the rapid radiation of this arid-adapted lizard throughout this vast territory. Subsequently, the geological events (e.g., uplift of the Hissar-Alay, transgressions of the Caspian Sea) and geographic barriers (e.g., Amu Darya River, Zeravshan River) during the Pleistocene triggered the progressive diversification of P. helioscopus. Interestingly, Clade VIII (P. helioscopus varius) experienced rapid population growth coupled with range expansion while Clade IV (P. helioscopus cameranoi) underwent drastic population expansion associated with range contraction during the Last Glacial Maximum. In Clade IV, but not in Clade VIII, environmental turnover contributes more to mitochondrial genetic distinctiveness than geographic distance. Overall, the SNP dataset demonstrates that geographic distance plays a greater role than environmental distance. Both the mtDNA dataset and the SNP dataset suggest local-scale genetic differentiation in Clade IV and Clade VIII, revealing potential geographic barriers in the Ili River Valley and the Junggar Basin, respectively. Twenty-seven outlier SNPs associated with environmental factors (precipitation and temperature) were identified, which supports the signature of local adaptation to the arid desert environment. Finally, our finding suggests taxonomic implications, such as support for full species status for P. saidalievi (Clade II) and P. meridionalis (Clade I). Future analyses based on further evidence and increased taxon and geographic sampling should be carried out to corroborate our findings.

Names, diagnoses and ‘Dead Names’: the case of Synedra pelagica

The case of Synedra pelagica Hendey is discussed in terms of its nomenclature, the taxonomic implications of priority issues and its characterization. Application of replacement names for specific epithets is reasonably straightforward as it is governed by the ICN – conditions for valid publication of any taxonomic name can be satisfied even if no one can subsequently identify the taxon. The lack of clear diagnostic characters, as opposed to a description, can obscure what the name actually represents. These issues are briefly discussed with Synedra pelagica in mind.

An update and review of commensals on Chilean inland water Decapoda

Abstract The commensals on Chilean Decapoda of inland waters are characterized by a marked microendemism. The aim of the present study was to do an exhaustive review on the ectocommensals on Chilean inland-water decapods. The literature revealed the presence of species of Protozoa, viz., eight known only from Parastacus pugnax (Lagenophrys andos, Operculigera insolita, O. parastacis, O. seticola, O. striata, O. taura, Chilenophrys allendei, and Circolagenophrys shiftus), one for both P. pugnax and P. nicoletti (L. anticthos), one for Parastacus pugnax and Samastacus spinifrons (O. asymmetrica), and one reported for Aegla laevis (O. velata). In addition, the presence of flatworms was described, specifically Temnocephala chilensis, associated with A. laevis, P. pugnax, and S. spinifrons, and species of Polychaeta, i.e., Stratiodrilus platensis associated with A. abtao and A. bahamondei, S. aeglaphilus for A. laevis, and S. pugnaxi for P. nicoletti. Biogeographical, ecological and taxonomic implications are discussed.

DNA barcoding of Chinese snakes reveals hidden diversity and conservation needs.

DNA barcoding has greatly facilitated studies of taxonomy, biodiversity, biological conservation, and ecology. Here, we establish a reliable DNA barcoding library for Chinese snakes, unveiling hidden diversity with implications for taxonomy, and provide a standardized tool for conservation management. Our comprehensive study includes 1638 cytochrome c oxidase subunit I (COI) sequences from Chinese snakes that correspond to 17 families, 65 genera, 228 named species (80.6% of named species) and 36 candidate species. A barcode gap analysis reveals gaps, where all nearest neighbour distances exceed maximum intraspecific distances, in 217 named species and all candidate species. Three species-delimitation methods (ABGD, sGMYC, and sPTP) recover 320 operational taxonomic units (OTUs), of which 192 OTUs correspond to named and candidate species. Twenty-eight other named species share OTUs, such as Azemiops feae and A. kharini, Gloydius halys, G. shedaoensis, and G. intermedius, and Bungarus multicinctus and B. candidus, representing inconsistencies most probably caused by imperfect taxonomy, recent and rapid speciation, weak taxonomic signal, introgressive hybridization, and/or inadequate phylogenetic signal. In contrast, 43 species and candidate species assign to two or more OTUs due to having large intraspecific distances. If most OTUs detected in this study reflect valid species, including the 36 candidate species, then 30% more species would exist than are currently recognized. Several OTU divergences associate with known biogeographic barriers, such as the Taiwan Strait. In addition to facilitating future studies, this reliable and relatively comprehensive reference database will play an important role in the future monitoring, conservation, and management of Chinese snakes.

Morphological Study of the Alimentary Canal and Malpighian Tubules in the Adult of the Pollen Beetle Meligethes (Odonthogethes) chinensis (Coleoptera: Nitidulidae: Meligethinae)

Meligethes (Odonthogethes) chinensis is a highly specialized species of Nitidulidae in China that takes pollen as its main food source, and its main host plant is Rubus idaeus L. (Rosaceae). In this study, the structural morphology of the alimentary canal and Malpighian tubules of adult M. (O.) chinensis was observed under light, fluorescence, and scanning electron microscopy. The alimentary canal of adult M. (O.) chinensis is divided into foregut, midgut, and hindgut. The foregut is the shortest and consists of the pharynx, esophagus, proventriculus, and cardiac valve. The midgut is a straight, distended, cylindrical, thin-walled tube. Numerous blunt-fingered gastric ceca are distributed irregularly throughout the midgut. The hindgut is subdivided into the ileum, colon, and rectum. The ileum is coiled. The colon gradually enlarges posteriorly. The rectum is thickly muscled and followed by a membranous structure. The openings of proximal Malpighian tubules are evenly inserted into the junction of the midgut and hindgut, and distal Malpighian tubules are evenly attached to the colon to form a cryptonephridial system. In this study, we also compare the structure and infer the function of the alimentary canal and Malpighian tubules among beetles, as well as discuss the evolutionary and taxonomical implications.

Growth patterns of palaeoscolecid sclerites from the Furongian (upper Cambrian) Wangcun section, western Hunan, South China

In a strict sense, palaeoscolecids are a group of cycloneuralian worms (ecdysozoans) characterized by the tessellation of trunk sclerites, which are differentiated into plates, platelets, and microplates. The Wangcun section in western Hunan, South China, which represents the Furongian Series (upper Cambrian), has yielded a rich and diverse collection of palaeoscolecids. However, there is uncertainty about how the morphology and arrangement of their sclerites change during ontogeny and the potential taxonomic implications of these changes. Here, we report new phosphatized trunk fragments from the Wangcun section, which are assigned to Dispinoscolex decorus, Hunanoscolex campus (= Ornatoscolex hunanensis), and Schistoscolex hunanensis. Trunk fragments of the same species with different diameter indicate the presence of several ontogenetic stages, and careful assessment revealed two types of sclerite growth patterns. One is represented by D. decorus and possibly also by S. hunanensis, in which the worm growth is accompanied mainly by the enlargement of the plates, with almost no change in the median annular zones and annulation boundaries. The other type is represented by H. campus, in which the worm growth is accompanied mainly by the widening of the median annular zones and annulation boundaries inserted with continuously more platelets and microplates. Because the specimens originally assigned to H. campus seem to represent late ontogenetic stages of O. hunanensis, we propose that H. campus is a senior synonym of the latter. This study underscores the importance of ontogenetic variation of sclerites for the taxonomy of palaeoscolecids, and highlights the significance of Orsten-type fossils in the study of metazoan ontogeny.

Palyno-taxonomic approach through light and scanning electron microscopy for the identification of herbaceous Asteraceae species from Sikaram Mountain Pak-Afghan border.

Due to the diverse and rich taxa, Asteraceae needs to explore from the untouched area. In this study, the pollen study was intended to assess the taxonomic value for Asteraceous taxa growing on the Sikaram Mountain Pak-Afghan border. Both microscopic techniques (LM and SEM) play a significant role in the identification and classification of herbaceous species of Asteraceae for their taxonomic and systematic implication. Pollen was observed and measured for the 15 species of Asteraceae. For investigated taxa 15 pollen characters with size, shape, polar view, pollen type, aperture orientation, and exine sculpturing in the eurypalynous pollen. Consequently, the pollen grains are usually Tricolporate, triangular to circular in polar view, while, the shape of pollen varies from subulate, oblate, and prolate along with prolate to spheroidal whereas, sculpturing also varies from Scabrate to micro reticulate, echino-perforate, Scabrate to echinate, echinate to granulate and echinate were observed. Similarly, among the quantitative data minimum values of polar and equatorial were 15.8 ± 0.74 μm in Filago pyramidata and 17.85 ± 0.39 μm in Heteropappus altaicus was measured respectively, while; the length of the spine with the least value of 2.45 ± 0.31 μm in Hertia intermedia and highest with 7.55 ± 0.31 μm was observed in Cirsium wallichii. The Exine thickness is a minimum of 1.70 ± 0.35 μm in Launaea nudicaulis and a maximum of 5.65 ± 3.59 μm in Cirssium vulgare. In addition, the highest pollen fertility (87%) in Centaurea iberica while the highest pollen sterility (32%) was recorded in Cirsium verutum. Furthermore, clustering via UPGMA, PCA, and PCoA analysis was performed for the separation of closely related taxa. It is concluded from this research work that palynological study has a crucial role in taxonomic, pure, and applied sciences. This study can be further authenticated and improved by a Phylogenetic study based on chloroplast DNA analysis & whole genome sequencing. RESEARCH HIGHLIGHTS: Pollen ultrastructure among 15 Asteraceous taxa. Micromorphological attributes measured via LM and SEM. Exine sculpture elements patterns provide accurate identification. Taxonomic keys were developed for its systematics implications.

<i>Chrysoritis</i> Butler (Papilionoidea: Lycaenidae: Aphnaeinae) – Part I: Molecular phylogenetic analyses of a South African genus of myrmecophilous butterflies

The molecular data of Talavera et al. (2020) is re-analysed to provide a foundation for a taxonomic revision of Chrysoritis. A COI phylogeny recovers most of the Chrysoritis species as monophyletic, and a few as polyphyletic but supported by the CAD gene. In the thysbe clade, most species, despite occurring in sympatry with at least one other species in the clade, maintain distinctive wing facies and ecological identity without intermediate forms. Within the thysbe clade, which contains the majority of species, sister taxon comparisons based on the COI phylogeny suggest speciation has been predominantly allopatric and accompanied mostly by minor morphological change and sometimes also a change in male patrolling terrain and/or host ant species. The diversification of the thysbe clade and the taxonomic implications of our results are discussed.

Palynomorphological Observations on the Genus Sabulina Rchb. (Caryophyllaceae) from Turkey Using Light Microscopy and Scanning Electron Microscopy.

Pollen morphology of 28 taxa belonging to the genus Sabulina Rchb. (Caryophyllaceae) from Turkey was examined and compared using light microscopy and scanning electron microscopy. The current study aimed to describe the palynological characteristics of the Sabulina taxa and to assess the diagnostic value of these features for taxonomic implications. The pollen grains of Sabulina are radially symmetrical, apolar, rarely isopolar, and pantopolyporate with 8-28 pores. Their shape is prolate-spheroidal with the A axes (long axes) 19.5 μm and the B axes (short axes) 19-39.5 μm. Exine sculpturing is microechinate-punctate in all taxa. Principal component analysis was used to evaluate the significant pollen morphological characters for distinguishing the taxa, with three components accounting for 95.112% of the total variance. Numerical analysis revealed that pollen sizes, pore diameters, pore numbers, distance between pores, spinule density, and punctum numbers are particularly the most useful variables for separating the Sabulina taxa. The results also display a partial relationship between the Sabulina taxa clusters based on pollen morphology and the systematics of these taxa based on general macromorphology.

North–South Differentiation of Black Flies in the Western Cordillera of North America: A New Species of Prosimulium (Diptera: Simuliidae)

Glaciation has been a powerful determiner of species distributions and the genetic structure of populations. Contemporary distributions of many organisms in North America’s Western Cordillera reflect the influence of Pleistocene glaciation. We identified a pattern of north–south differentiation in the genus Prosimulium of western North America, which reflects the separation of northern and southern populations by the North American Ice Sheet during the Pleistocene Epoch. The taxonomic implication is that new species exist within nominal species, requiring formal description or revalidation of names currently in synonymy. We morphologically and cytogenetically examined populations of one nominal species of black fly, Prosimulium esselbaughi Sommerman, over its known range from Alaska south to California and Colorado. Chromosomal and morphological evidence supports the presence of two species, P. esselbaughi sensu stricto from Alaska to at least southern British Columbia, and a new species, Prosimulium supernum in the central Rocky Mountains and high Sierra Nevada range of the United States. The new species is described in all life stages above the egg, along with its polytene chromosomes. The existence of differentiated populations of other nominal species of black flies in northern and southern North America provides a system for investigating possible co-differentiation of vectors and parasites.

Pectins, hemicellulose and lignocellulose profiles vary in leaves among different aromatic Vanilla species (Orchidaceae)

The alcohol-insoluble residue in Vanilla dressleri, V. odorata, V. planifolia and V. pompona mature leaves was fractionated into water-, oxalate-, HCl- and NaOH-soluble pectins, hemicellulose and lignocellulose. Neutral sugars and uronic acids of each fraction were determined by high-performance anion exchange chromatography-pulsed amperometric detection. V. dressleri differentiated from the other three species based on the higher amounts of the HCl-soluble pectin fraction and the amount of glucose exceeding 5–7 times the values found in the NaOH-soluble pectin fraction in the other species, as well as a cellulose/hemicellulose ratio of ca. 2/3. Analogously, V. planifolia could also be distinguished by its higher cellulose/hemicellulose ratio of ca. 7. In addition to taxonomical implications, these results might be instrumental for defining adequate conditions for cell wall digestion aiming at protoplast isolation and appropriate media composition for cell wall regeneration during protoplast culture, which has been elusive in the Orchidaceae.

Cranial osteology of the basal megatherioid sloth Schismotherium (Mammalia, Xenarthra) and its taxonomic implications

ABSTRACT This study comprises a comparative description of the skull anatomy in the basal megatherioid sloth Schismotherium fractum, based on specimens from the Santa Cruz Formation (late early Miocene; Santacrucian SALMA) in southern Argentine Patagonia. We provide more detailed descriptions and illustrations of the skull bones and their sutural connections, as well as the cranial foramina and their contents, than have previously been available. The anatomy in S. fractum is compared to contemporaneous basal megatherioids from Santa Cruz, Hapalops elongatus and Pelecyodon cristatus. The latter is a close relative of S. fractum in several phylogenetic analyses, but given the high levels of anatomical variation and other taxonomic uncertainties that surround these sloths, previous authors have suggested that the two may not represent distinct taxa. Our observations demonstrate that although the skulls of S. fractum do indeed exhibit variation in a broad variety of features, there are invariant, apomorphic features that consistently distinguish Schismotherium and Pelecyodon from one another, including at least 17 features derived from virtually every region of the skull. While supporting the current taxonomic status of these important, basal-most megatherioids, the present study highlights the need for further anatomical and phylogenetic investigations of Santacrucian sloths.

Taxonomic revision of Hypochaeris (Compositae: Cichorieae) in Uruguay

The taxonomic revision of Hypochaeris L. (Compositae: Cichorieae) for Uruguay is presented. Specimens from the main herbaria of the country were reviewed, field trips were carried out to study the species “in situ” throughout the country, and all reference publications and original material for each species were reviewed. A list of all species present in Uruguay is included together with their respective synonyms, expanded descriptions, distribution maps, habitat and phenological data, taxonomic and nomenclatural observations, as well plates with images and illustrations highlighting the most relevant morphological characters of each. Additionally, dichotomous and virtual keys are provided for the identification of the sections, series and species of the genus in Uruguay. The genus Hypochaeris in Uruguay comprises 11 species, two exotic (Hypochaeris sect. Hypochaeris), and nine native to the territory (Hypochaeris sect. Phanoderis), two of which are considered priorities for conservation in Uruguay. The name H. rosengurttii is reinstated as a species and the species H. pampasica is recorded for the first time in the country, while H. lutea and H. neopinnatifida are excluded. The taxonomic complexities surrounding the name H. microcephala are discussed, as well as the presence of hybrid taxa within the genus and their taxonomic implications.