An unusual new archosauriform from the Middle–Late Triassic of southern Brazil and the monophyly of Doswelliidae

Until now the Doswelliidae was considered a monospecific family including Doswellia kaltenbachi from the Late Triassic of North America. The phylogenetic position of this taxon remained enigmatic until recently, when a sister‐group relationship with the Proterochampsidae was suggested. In the present contribution we describe the new doswelliid species Archeopelta arborensis gen. et sp. nov. from the Middle–Late Triassic of Brazil. A cladistic analysis recovered Archeopelta, Doswellia, and Tarjadia within a monophyletic group of basal archosauriforms, the Doswelliidae. The monophyly of this family is supported by the presence of osteoderm ornamentation that is coarse, incised, and composed of regular pits and the presence of an unornamented anterior articular lamina. Archeopelta is more closely related to Doswellia than to other archosauriforms by the presence of basipterygoid processes anterolaterally orientated, dorsal centra with a convex surface, width of the neural arch plus ribs of the first primordial sacral that are three times the length of the neural arch, and iliac blade laterally deflected, with strongly convex dorsal margin, and a length less than three times its height. The phylogenetic analysis indicates that Doswellidae is the closest large monophyletic entity to Archosauria, which achieved a wide palaeolatitudinal distribution during the late Middle and Late Triassic time span. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 161 , 839–871.     

A new nothrotheriid xenarthran from the early Pliocene of Pomata‐Ayte (Bolivia): new insights into the caniniform–molariform transition in sloths

Tardigrade xenarthrans are today represented only by the two tree sloth genera Bradypus and Choloepus, which inhabit the Neotropical rainforests and are characterized by their slowness and suspensory locomotion. Sloths have been recognized in South America since the early Oligocene. This monophyletic group is represented by five clades traditionally recognized as families: Bradypodidae, Megalonychidae, Mylodontidae (?), Megatheriidae (?) and Nothrotheriidae (?). A new nothrotheriid ground sloth represented by a dentary and several postcranial elements, Aymaratherium jeani gen. nov. , sp. nov. , from the early Pliocene locality of Pomata‐Ayte (Bolivia) is reported. This small‐ to medium‐sized species is characterized especially by its dentition and several postcranial features. It exhibits several convergences with the ‘aquatic’ nothrotheriid sloth Thalassocnus and the giant megatheriid ground sloth Megatherium (M.) americanum, and is interpreted as a selective feeder, with good pronation and supination movements. The tricuspid caniniform teeth of Aymaratherium may represent a transitional stage between the caniniform anterior teeth of basal megatherioids and basal nothrotheriids (1/1C‐4/3M as in Hapalops or Mionothropus) and the molariform anterior teeth of megatheriids (5/4M, e.g. Megatherium). To highlight the phylogenetic position of this new taxon among nothrotheriid sloths, we performed a cladistic assessment of the available dental and postcranial evidence. Our results, derived from a TNT treatment of a data matrix largely based on a published phylogenetic data set, indicate that Aymaratherium is either sister taxon to Mionothropus or sister to the clade Nothrotheriini within Nothrotheriinae. They further support the monophyly of both the Nothrotheriinae and the Nothrotheriini, as suggested previously by several authors.     

The phylogeny of Anophelinae revisited: inferences about the origin and classification of Anopheles (Diptera: Culicidae)

The evolution of anopheline mosquitoes (Culicidae: Anophelinae) has been the subject of speculation and study for decades, but a comprehensive phylogeny of these insects is far from complete. The results of phylogenetic studies based on morphological and molecular data sets are conspicuously ambiguous. Here, we revisit the phylogenetic relationships of anopheline mosquitoes using state‐of‐the‐art software and cladistic methods to analyse the data set of Harbach & Kitching (2005). We present a refined interpretation of relationships based on analyses of a revised data set that includes an additional species. Implied weighting analyses were conducted with TNT with the concavity constant K ranging from 1 to 33. We determined the optimal K value by summing the GC supports for each MPC and selected the tree with the highest support, K = 30, as the preferred cladogram. We then collapsed the branches with GC support < 1 to obtain the ‘best’ topography of relationships. Genus Chagasia is the basalmost taxon of Anophelinae, and genus Anopheles is recovered as monophyletic but only if Anopheles implexus is excluded and genus Bironella is subordinated within it. The Afrotropical An. implexus is recovered as the sister to all other anophelines, and Christya Theobald, stat. nov., is elevated from synonymy with Anopheles Meigen as a subgenus to accommodate it. The other anophelines comprise two large clades. The first includes the reciprocally monophyletic subgenera Kerteszia + Nyssorhynchus; the second consists of subgenus Cellia as the sister to a heterogeneous clade that includes genus Bironella and subgenera Anopheles, Baimaia, Lophopodomyia and Stethomyia of genus Anopheles. The sister relationship of Cellia and the heterogeneous clade is lost when the branches with GC <1 are collapsed. The monophyly and non‐monophyly of the informal subordinate taxa of subgenera Nyssorhynchus, Cellia and Anopheles, and also evolutionary scenarios, are discussed in relation to previous studies.     

A total evidence analysis of the phylogeny of hatchet-faced treefrogs (Anura: Hylidae: Sphaenorhynchus)

The Neotropical hylid genus Sphaenorhynchus includes 15 species of small, greenish treefrogs widespread in the Amazon and Orinoco basins, and in the Atlantic Forest of Brazil. Although some studies have addressed the phylogenetic relationships of the genus with other hylids using a few exemplar species, its internal relationships remain poorly understood. In order to test its monophyly and the relationships among its species, we performed a total evidence phylogenetic analysis of sequences of three mitochondrial and three nuclear genes, and 193 phenotypic characters from all species of Sphaenorhynchus. Our results support the monophyly of Sphaenorhynchus with molecular and phenotypic evidence, with S. pauloalvini as the earliest diverging taxon, followed by S. carneus, as the sister taxon of all remaining species of the genus. We recognize three species groups in Sphaenorhynchus (the S. lacteus, S. planicola and S. platycephalus groups), to facilitate its taxonomic study; only three species (S. carneus, S. pauloalvini and S. prasinus) remain unassigned to any group. Sequence data were not available for only two species (S. bromelicola and S. palustris) for which we scored phenotypic data; wildcard behaviour was detected only in S. bromelicola nested inside the S. platycephalus group. On the basis of the resulting phylogenetic hypothesis, we discuss the evolution of oviposition site and a number of phenotypic characters that could be associated with heterochronic events in the evolutionary history of this group.     

Mitogenomic phylogenetics of Diochus occultus n. sp., a palaeoendemic endogean species within the tribe Diochini (Coleoptera: Staphylinidae: Staphylininae)

The tribe Diochini has a worldwide distribution, with 2 and 74 epigean species within the genera Antarctothius and Diochus, respectively. Recent phylogenetic studies suggest a sister relationship of Diochini and a lineage formed by Xantholinini, Maorothiini, and Othiini, within the subfamily Staphylininae. Here, we describe the first known endogean representative of Diochini, Diochus occultus n. sp., and provide the first two complete mitogenomes for the tribe, corresponding to the two European Diochus species: Diochus occultus n. sp. and Diochus staudingeri. These sequences were combined with 40 additional mitogenomes from representatives within Staphylininae, Paederinae, Silphidae, and Aleocharinae, and COI sequences from 5 additional species of Diochus to conduct a series of mitogenomic phylogenetic and dating analyses. The estimated molecular phylogeny is fully consistent with previous studies based on morphology and molecular data, finding a sister relationship of Diochini with a clade formed by Xantholinini and Othiini (Maorothiini not sampled). Dating analyses inferred an early split of the tribe Diochini at 140–156 Mya. Morphology shows clear differences in the aedeagal and external morphology of D. occultus n. sp. and D. staudingeri, whereas a sister relationship of these taxa is found in the phylogenetic analyses, with the split dated at 48–61 Mya. Although the study of additional Palaearctic Diochus species will be required to conclusively establish that D. occultus n. sp. is a palaeoendemic taxon sister to D. staudingeri, associated with forests of Abies pinsapo in the south of the Iberian Peninsula, this conclusion is consistent with the ancient estimated age of speciation, endogean habitat specificity, low dispersal capacity (flightless species), and microendemicity of D. occultus. This is also consistent with the continued emersion of the Betic sub‐plate along its tectonic evolution. The estimated ages of diversification of the Paederinae‐Staphylininae lineage are also discussed.     

The Phylogeny of the Myrmecophagidae (Mammalia, Xenarthra, Vermilingua) and the Relationship of Eurotamandua to the Vermilingua

A cladistic investigation of the phylogenetic relationships among the three extant anteater genera and the three undoubted extinct myrmecophagid genera is performed based upon osteological characteristics of the skull and postcranial skeleton. One hundred seven discrete morphological characters are analyzed using the computer program PAUP. Characters are polarized via comparison to the successive xenarthran outgroups Tardigrada (represented by the living sloth Bradypus) and Cingulata (represented by the recent armadillos Dasypus and Euphractus). The analysis results in a single most-parsimonious tree (TL = 190, CI = 0.699, RI = 0.713). The tree corroborates the monophyly of the subfamilies Cyclopinae and Myrmecophaginae, the former including the extant Cyclopes and the Pliocene genus Palaeomyrmidon. Within the Myrmecophaginae the Miocene genus Protamandua is the sister taxon to a clade including the remaining three genera. The recent Tamandua is in turn the sister taxon to the extant Myrmecophaga plus the Pliocene genus Neotamandua. Contrary to the suggestions of recent authors, weak support is provided for the taxonomic distinctiveness of the latter genus from the recent Myrmecophaga. The monophyly of the Myrmecophagidae is supported by 15 unequivocal synapomorphies. The monophyly of the Cyclopinae and Myrmecophaginae is supported by 3 and 13 unambiguous synapomorphies, respectively. The enigmatic Eocene genus Eurotamandua, from the Messel fauna of Germany, is coded for the 107 morphological characters above and included in two subsequent PAUP analyses. The palaeanodont Metacheiromys is also added to these two analyses as a nonxenarthran outgroup to test for the possibility that Eurotamandua lies outside the Xenarthra. In the first analysis, Eurotamandua is constrained a priori to membership in the Vermilingua. The single most-parsimonious tree (TL = 224, CI = 0.618) that results places Eurotamandua as the sister group to the remaining anteater genera, contra Storch and Habersetzer's (1991) assignment of Eurotamandua to the vermilinguan subfamily Myrmecophaginae. Eurotamandua shares six unequivocal synapomorphies with other anteaters, including the absence of teeth and the presence of a lateral tuberosity on the fifth metatarsal. The remaining vermilinguans are united by 11 unequivocal synapomorphies, plus an additional 10 ambiguous synapomorphies. In the second analysis, the position of Eurotamandua is unconstrained. The resulting single most-parsimonious tree (TL = 219, CI = 0.632) places Eurotamandua outside Vermilingua as the sister group to the Pilosa (Vermilingua plus Bradypus). The monophyly of this node is supported by four unambiguous synapomorphies in the unconstrained analysis. Further manipulation of this second analysis shows that placement of Eurotamandua as the sister group to the Xenarthra or to the Palaeanodonta adds three steps to the shortest tree but is more parsimonious than its placement as a sister group to the Vermilingua is the previous analysis. The addition of pangolins to the analysis does little to alter the major phylogenetic conclusions of the study. The allocation of Eurotamandua to the Xenarthra, but as a sister group to the Pilosa, is a novel arrangement which leaves open the biogeographic question of how a xenarthran reached Western Europe during the Eocene.     

PHYLOGENETIC ANALYSES OF THE BRYOPSIDALES (ULVOPHYCEAE,CHLOROPHYTA) BASED ON RUBISCO LARGE SUBUNIT GENE SEQUENCES1

Current taxonomy of the Bryopsidales recognizes eight families; most of which are further categorized into two suborders, the Bryopsidineae and Halimedineae. This concept was supported by early molecular phylogenetic analyses based on rRNA sequence data, but subsequent cladistic analyses of morphological characters inferred monophyly in only the Halimedineae. These conflicting results prompted the current analysis of 32 taxa from this diverse group of green algae based on plastid‐encoded RUBISCO large subunit (rbcL) gene sequences. Results of these analyses suggested that the Halimedineae and Bryopsidineae are distinct monophyletic lineages. The families Bryopsidaceae, Caulerpaceae, Codiaceae, Derbesiaceae, and Halimediaceae were inferred as monophyletic, however the Udoteaceae was inferred as non‐monophyletic. The phylogenetic position of two taxa with uncertain subordinal affinity, Dichotomosiphon tuberosus Lawson and Pseudocodium floridanum Dawes & Mathieson, were also inferred. Pseudocodium was consistently placed within the halimedinean clade suggesting its inclusion into this suborder, however familial affinity was not resolved. D. tuberosus was the inferred sister taxon of the Halimedineae based on analyses of rbcL sequence data and thus a possible member of this suborder.     

Proopiomelanocortin (POMC) and testing the phylogenetic position of turtles (Testudines)

Morphological and molecular studies have inferred multiple hypotheses for the phylogenetic relationships of Testudines. The hypothesis that Testudines are the only extant anapsid amniotes and the sister taxon of diapsid amniotes is corroborated by morphological studies, while the hypothesis that Testudines are diapsid amniotes is corroborated by more recent molecular and morphological studies. In this study, the placement of Testudines is tested using the full length cDNA sequence of the polypeptide hormone precursor proopiomelanocortin (POMC). Because only extant taxa have been used, the hypotheses being tested are limited to the following (1) Testudines as the sister taxon of Archosauria, (2) Testudines included in Archosauria and the sister taxon of Crocodilia, (3) Testudines as the sister taxon of Lepidosauria, (4) Testudines as the sister taxon of Sauria, and (5) Testudines as the sister taxon of a monophyletic Mammalia–Sauria clade. Neither Maximum likelihood, Bayesian, or maximum parsimony analyses are able to falsify the hypothesis of (Archosauria (Lepidosauria, Testudines)) and as such is the preferred inference from the POMC data.     

The Miocene tortoise Testudo catalaunica Bataller, 1926, and a revised phylogeny of extinct species of genus Testudo (Testudines: Testudinidae)

We provide a taxonomic review of the extinct testudinid Testudo catalaunica, based on published and unpublished material from several Miocene (late Aragonian and early Vallesian) sites of the Vallès‐Penedès Basin (north‐east Iberian Peninsula). We show that Testudo catalaunica irregularis is a junior subjective synonym of T. catalaunica, and further provide an emended diagnosis of the latter based on newly reported material. Contrary to some recent suggestions, this emended diagnosis discounts an alternative attribution of T. catalaunica to Paleotestudo. The latter is merely recognized as a subgenus of Testudo, based on a cladistic analysis that assessed the phylogenetic position of all extant and most extinct species of Testudo currently recognized as valid (including T. catalaunica). Our phylogenetic analysis (which recovers the molecular phylogeny of extant Testudo s.l.) supports a taxonomic scheme in which the three extant subgenera of Testudo are represented in the fossil record. Testudo s.s. is retrieved as the sister taxon of Testudo (Agrionemys) + [Testudo (Paleotestudo) + Testudo (Chersine)]. The extinct Testudo (Paleotestudo) is therefore the sister taxon of the Testudo (Chersine) clade. The latter subgenus reveals as the most diverse clade of Testudo s.l. in the fossil record, with T. catalaunica + Testudo steinheimensis constituting a subclade distinct from that including Testudo hermanni.     

Radiation of the Drosophila nannoptera species group in Mexico

The Drosophila nannoptera species group, a taxon of Mexican cactophilic flies, is an excellent model system to study the influence of abiotic and biotic factors on speciation, the genetic causes of ecological specialization and the evolution of unusual reproductive characters. However, the phylogenetic relationships in the nannoptera species group and its position within the virilis‐repleta phylogeny have not been thoroughly investigated. Using a multilocus data set of gene coding regions of eight nuclear and three mitochondrial genes, we found that the four described nannoptera group species diverged rapidly, with very short internodes between divergence events. Phylogenetic analysis of repleta group lineages revealed that D. inca and D. canalinea are sister to all other repleta group species, whereas the annulimana species D. aracataca and D. pseudotalamancana are sister to the nannoptera and bromeliae species groups. Our divergence time estimates suggest that the nannoptera species group radiated following important geological events in Central America. Our results indicate that a single evolutionary transition to asymmetric genitalia and to unusual sperm storage may have occurred during evolution of the nannoptera group.     

Evidence for the most basal split in land plants dividing bryophyte and tracheophyte lineages

The problem of relationships among the major basal living groups of land plants is long standing, yet the uncertainty as to the phylogenetic affinity of these lines persists in the literature. Molecular and modern cladistic studies of the phylogenetic relationships of the above groups resulted in a large number of conflicting topologies. However, with the exception of the cladistic analyses of spermatogenesis, suggesting monophyly of extant bryophytes, these studies agree the paraphyletic bryophyte grade is basal within the embryophyte tree. Here we would like to present analyses on the basis of the concatenated datasets of nucleotide and amino-acid sequences of 57 protein-coding genes common to 17 chloroplast genomes of land plants and a charophyte alga Chaetosphaeridium globosum. Character-wise, these are the largest datasets currently available to address the problem of basal relationships within embryophytes. Main lineages of bryophytes, i.e liverworts, hornworts and mosses are represented in our alignments with a single taxon, whereas 14 taxa represent the tracheophytes. With our data, phylogeny with liverwort basal appears to be and artifact related to high and unequal A+T contents among the sequences analysed. Reducing this compositional bias and applying methods developed to counter it, we recovered an alternative, strongly supported topology wherein both bryophytes and tracheophytes are monophyletic. Within bryophytes, hornworts are basal and liverworts are sister to mosses.     

Systematics of spiny‐backed treefrogs (Hylidae: Osteocephalus): an Amazonian puzzle

Spiny‐backed tree frogs of the genus Osteocephalus are conspicuous components of the tropical wet forests of the Amazon and the Guiana Shield. Here, we revise the phylogenetic relationships of Osteocephalus and its sister group Tepuihyla, using up to 6134 bp of DNA sequences of nine mitochondrial and one nuclear gene for 338 specimens from eight countries and 218 localities, representing 89% of the 28 currently recognized nominal species. Our phylogenetic analyses reveal (i) the paraphyly of Osteocephalus with respect to Tepuihyla, (ii) the placement of ‘Hyla’ warreni as sister to Tepuihyla, (iii) the non‐monophyly of several currently recognized species within Osteocephalus and (iv) the presence of low (<1%) and overlapping genetic distances among phenotypically well‐characterized nominal species (e.g. O. taurinus and O. oophagus) for the 16S gene fragment used in amphibian DNA barcoding. We propose a new taxonomy, securing the monophyly of Osteocephalus and Tepuihyla by rearranging and redefining the content of both genera and also erect a new genus for the sister group of Osteocephalus. The colouration of newly metamorphosed individuals is proposed as a morphological synapomorphy for Osteocephalus. We recognize and define five monophyletic species groups within Osteocephalus, synonymize three species of Osteocephalus (O. germani, O. phasmatus and O. vilmae) and three species of Tepuihyla (T. celsae, T. galani and T. talbergae) and reallocate three species (Hyla helenae to Osteocephalus, O. exophthalmus to Tepuihyla and O. pearsoni to Dryaderces gen. n.). Furthermore, we flag nine putative new species (an increase to 138% of the current diversity). We conclude that species numbers are largely underestimated, with most hidden diversity centred on widespread and polymorphic nominal species. The evolutionary origin of breeding strategies within Osteocephalus is discussed in the light of this new phylogenetic hypothesis, and a novel type of amplexus (gular amplexus) is described.     

Phylogenetic relationships of the Neotropical spider genus Itatiaya (Araneae)

Polotow, D. & Brescovit, A. D. (2010). Phylogenetic relationships of the Neotropical spider genus Itatiaya (Araneae). —Zoologica Scripta, 40, 187–193. A cladistic analysis using parsimony under equal weights is applied to test the phylogenetic relationships of Itatiaya Mello‐Leitão, previously described in Ctenidae. The data matrix comprised 25 taxa scored for a total of 47 characters. The cladistic analysis yielded two equally parsimonious trees of 124 steps. The consensus of the two most parsimonious trees is used to discuss the phylogenetic relationships and justify taxonomic modifications. The results indicate that this genus is a representative of Zoropsidae, which is newly recorded from the Neotropical region. The monophyly of Itatiaya is supported by three non‐ambiguous synapomorphies and three homoplastic synapomorphies. A new diagnosis is provided for Itatiaya. Itatiaya pucupucu is placed as sister species to the remaining species of the genus. A polytomic clade composed of Itatiaya modesta, Itatiaya iuba, Itatiaya apipema and the clade formed by Itatiaya tacamby + Itatiaya pykyyra is supported by the presence of modified cylindrical gland spigots. Additionally, the male of I. pykyyra Polotow & Brescovit is described for the first time.     

Contributions to molecular systematics of water scavenger beetles (Hydrophilidae,Coleoptera)

Phylogenetic relationships within Hydrophilidae were examined by analyses of separate and combined nuclear and mitochondrial markers (28S rRNA, 18S rRNA, 16S rRNA, 12S rRNA, COI and COII genes). The preferred (Bayesian) tree topology suggests a sister group relationship between Spercheidae and Hydrophilidae, supporting the ‘hydrophilid lineage’; Epimetopidae are placed on the base of the ‘helophorid branch’, the monophyly of Sphaeridiinae is highly supported, nested deeply within Hydrophilidae closest to Enochrus, making Hydrophilinae and Acidocerini paraphyletic; Hydrobius appears as sister taxon to (Hydrochara + Hydrophilus) without a closer relationship to Acidocerini; the hydrophiloid–histeroid sister group relationship is confirmed. The topology of several taxa remains contradictory, and requires further investigations with a larger taxon sampling and additional molecular markers.     

Evolution,biogeography and systematics of the western Palaearctic Zamenis ratsnakes

The phylogenetic relationships between western Palaearctic Zamenis and Rhinechis ratsnakes have been troubled, with recent estimates based on the supermatrix approach questioning their monophyly and providing contradictory results. In this study, we generated a comprehensive molecular data set for Zamenis and closely related ratsnakes to assess their phylogenetic and systematic relationships and infer their spatial and temporal modes of diversification. We obtained a fully resolved and well‐supported phylogeny, which is consistent across markers, taxon‐sets and phylogenetic methods. The close phylogenetic relationship between Rhinechis and Zamenis is well‐established. However, the early branching pattern within this clade, and the position of R. scalaris and Z. hohenackeri, remains poorly supported. The Persian ratsnake Z. persicus is sister to the Mediterranean species Z. situla, Z. longissimus and Z. lineatus, of which Z. situla is sister to a clade containing the latter two species. These results are consistent with a recent phylogenomic study on ratsnakes based on hundreds of loci. Whereas, topological tests based on our data and evidence from such phylogenomic study strongly rejected previous phylogenetic estimates based on the supermatrix approach and demonstrate that these “mega‐phylogenies”, with hundreds of taxa and high levels of missing data, have recovered inconsistent relationships with spurious nodal support. Biogeographical and molecular dating analyses suggest an origin of the ancestor of Rhinechis and Zamenis in the Aegean region with early cladogenesis during the Late Miocene associated with the Aegean arch formation and support a scenario of east‐to‐west diversification. Finally, while we have little morphological and phylogenetic evidence for the distinctiveness between Rhinechis and Zamenis, a classification of them in a single genus, and the designation of Zamenis scalaris (Schinz, 1822), reflects better their evolutionary relationships.     

A preliminary phylogenetic study of Megapodagrionidae with focus on the Chinese genera <Emphasis Type="Italic">Sinocnemis</Emphasis> Wilson &; Zhou and <Emphasis Type="Italic">Priscagrion</Emphasis> Zhou &; Wilson (Odonata: Zygptera)

A cladistic analysis of the megapodagrionid damseflies was performed on a data matrix of 44 morphological characters and 39 terminal taxa with emphasis on defining the phylogenetic position of the Chinese genera Sinocnemis Wilson & Zhou and Priscagrion Zhou & Wilson which have rarely been used in a cladistic study before. Sinocnemis is recovered as the sister group to all other reduced-venation groups, including Chorismagrion + Perissolestes, Hemiphlebia, and all coenagrionoids; Priscagrion is close to Austroargiolestes. Sinocnemis henanensis is confirmed as a good species.     

Haemothermia or Archosauria? The interrelationships of mammals,birds and crocodiles

The recently proposed hypothesis that the living birds and the living mammals are sister groups, together forming a natural taxon Haemothermia, is contrasted with the more traditional view, that birds and crocodiles are living sister groups within the taxon Archosauria. Of the 28 or so characters claimed to be unique to the Haemothermia, several are found to be structurally or developmentally different in birds compared to mammals. Others are found to occur also in crocodiles. In either case the status of the characters as homologues categorizing the group becomes doubtful, and only about eight characters remain as potentially acceptable. In contrast, some 24 characters are identified as potential homologues of birds plus crocodiles and therefore categorizing the group Archosauria, and this hypothesis must be judged preferable. The evidence of the characters of fossils can be used legitimately to test cladograms, but only to a limited extent. Nevertheless, the relevant fossils do support the Archosauria rather than the Haemothermia hypothesis. Cladograms logically may, and methodologically should, be taken as theories of phylogenetic relationships, and are potentially subject to independent evolutionary tests. A priori character weighting is sound in principle but cannot be applied in practice for want of the necessary, independently acquired knowledge of how characters change in evolution. The relative dates of the fossils is shown to be more compatible with the Archosauria than the Haemothermia classification. Finally, the hypothetical common ancestors that are implied by the two respective cladograms are compared. That shared by mammals and birds, as implied by the Haemothermia theory, would have been functionally incongruent, and therefore less probable than that shared by birds and crocodiles. These several lines of evidence all lead to the conclusion that the traditional theory of a relationship between birds and crocodiles, vis à vis mammals is substantially the better supported.