Two braincases of Daspletosaurus (Theropoda: Tyrannosauridae): anatomy and comparison1

For sheer complexity, braincases are generally considered anatomically conservative. However, recent research on the braincases of tyrannosaurids have revealed extensive morphological variations. This line of inquiry has its root in Dale Russell’s review of tyrannosaurids in which he established Daspletosaurus torosus — a large tyrannosaurine from the Campanian of southern Alberta. In the wake of systematic revisions to tyrannosaurines previously assigned to Daspletosaurus, one potentially distinct species remains undescribed. This paper describes and compares a braincase referable to this species with that of the holotype for Daspletosaurus torosus using computerized-tomography-based reconstructions. The two braincases have numerous differences externally and internally. The specimen of Daspletosaurus sp. has a bottlenecked olfactory tract, short and vertical lagena, and a developed ascending column of the anterior tympanic recess. The holotype of Daspletosaurus torosus has many unusual traits, including an anteriorly positioned trochlear root, elongate common carotid canal, distinct chamber of the basisphenoid recess, asymmetry in the internal basipterygoid aperture, and laterally reduced but medially expanded subcondylar recess. This comparison also identified characters that potentially unite the two species of Daspletosaurus, including deep midbrain flexures in the endocasts. However, many character variations in the braincases are known in other tyrannosaurids to correlate with body size and maturity, or represent individual variations. Therefore, taxonomic and phylogenetic signals can be isolated from background variations in a more comprehensive approach by using additional specimens. New information on the two braincases of Daspletosaurus is consistent with the emerging view of tyrannosaurid braincases as highly variable, ontogenetically dynamic character complexes.

Paleotelmatoscopus, a proposed new genus for some fossil moth flies (Diptera, Psychodidae, Psychodinae) in Eocene Baltic amber, with description of a new species

Few species of Baltic amber Psychodinae have been described to date. Some were incorrectly classified in Pericoma Walker based on an early, broad definition of the genus and holotypes were not specified. We examined approximately 50 specimens of Baltic amber Psychodinae in addition to reviewing the original series studied by Fernand Meunier. Lectotypes for Pericoma formosa Meunier and P. speciosa Meunier are designated and Paleotelmatoscopus gen. nov. is proposed to include P. formosa and P. madrizi sp. nov. Characters included in the diagnosis of this new genus and species have implications for future descriptions of Baltic amber Psychodinae. Parts of the head capsule, such as antennae, are often well-preserved and visible, and can be useful for separating species. However, these character complexes are prone to homoplasy and should not be used alone to define genera. Since it is impossible to view internal genitalic characters in fossil species, refinement of generic and species diagnoses based on external morphology is a critical factor in describing the amber fauna.

Rodent Suborders

For two hundred years the status of rodent suborders has been unstable. What are the natural groupings of extant rodent families? The formal recognition of rodent suborders has remained challenging and consensus has been elusive. Classically conceived rodent suborders are widely viewed as artificial, but no universally accepted classification has emerged to reflect the major features of rodent evolution. Over the last two decades molecular studies have established that extant rodents comprise three monophyletic clades. We review the molecular basis for these groups and recognize them as taxonomic units: Suborder Ctenohystrica Huchon et al., 2000, Suborder Supramyomorpha D’Elía et al., 2019, and a group of families clustered with Sciuridae. The latter differs from Sciuromorpha as traditionally conceived because the suborder includes Aplodontiidae but excludes Castoridae. We review morphological character complexes that are distributed broadly within these three clades, name the third group Eusciurida, new suborder, and find this three-fold division of extant Rodentia to reflect well the major features of rodent phylogeny. That some morphological features do not characterize all families within suborders, or are not unique to individual suborders, indicates major parallel innovations and reversals in rodent evolution. These incongruent morphologies invite future study.

Caste-specific morphological modularity in the ant tribe Camponotini (Hymenoptera, Formicidae)

Background The morphological structures of organisms form tightly integrated but mutually independent character complexes (modules) linked through common development and function. Even though their abundance, diversity, and complex caste systems make camponotine ants ideal subjects to research developmental modularity and phenotypic integration, no studies investigating these phenomena have been conducted in this taxonomic group. This study attempts to identify and visualize integrated character complexes in 14 taxa from the genera Camponotus and Colobopsis using statistical analyses of morphometry. Results The identified modules differ between castes: Minor workers have small heads and long extremities, while major workers have enlarged heads modified for defence, and short, thick appendages; extremities (legs and antennae) are strongly correlated in both worker castes. Gynes show weaker integration of extremities, but a strong correlation of mesosoma and eyes, and highly variable median ocellus size. Gynes infested by mermithid nematodes exhibit reduction of gyne-specific characters and altered patterns of phenotypic integration. Conclusion The integrated character complexes described herein can largely be interpreted as functional, caste-specific modules related to behavioural ecology and task allocation within ant colonies. This modular nature of the body plan is hypothesized to facilitate the evolution of novel phenotypes and thus contributes to the tremendous evolutionary success of ants. The study of these modules can help to further elucidate the evolution and ontogeny of castes in camponotine ants, as well as the effects of parasite infestation on the phenotype.

Phylogeny of Paleozoic limbed vertebrates reassessed through revision and expansion of the largest published relevant data matrix

The largest published phylogenetic analysis of early limbed vertebrates (Ruta M, Coates MI. 2007.Journal of Systematic Palaeontology5:69–122) recovered, for example, Seymouriamorpha, Diadectomorpha and (in some trees) Caudata as paraphyletic and found the “temnospondyl hypothesis” on the origin of Lissamphibia (TH) to be more parsimonious than the “lepospondyl hypothesis” (LH)—though only, as we show, by one step. We report 4,200 misscored cells, over half of them due to typographic and similar accidental errors. Further, some characters were duplicated; some had only one described state; for one, most taxa were scored after presumed relatives. Even potentially continuous characters were unordered, the effects of ontogeny were not sufficiently taken into account, and data published after 2001 were mostly excluded. After these issues are improved—we document and justify all changes to the matrix—but no characters are added, we find (Analysis R1) much longer trees with, for example, monophyletic Caudata, Diadectomorpha and (in some trees) Seymouriamorpha;Ichthyostegaeither crownward or rootward ofAcanthostega; and Anthracosauria either crownward or rootward of Temnospondyli. The LH is nine steps shorter than the TH (R2; constrained) and 12 steps shorter than the “polyphyly hypothesis” (PH—R3; constrained).Brachydectes(Lysorophia) is not found next to Lissamphibia; instead, a large clade that includes the adelogyrinids, urocordylid “nectrideans” and aïstopods occupies that position. As expected from the taxon/character ratio, most bootstrap values are low. Adding 56 terminal taxa to the original 102 increases the resolution (and decreases most bootstrap values). The added taxa range in completeness from complete articulated skeletons to an incomplete lower jaw. Even though the lissamphibian-like temnospondylsGerobatrachus,MicropholisandTungussogyrinusand the extremely peramorphic salamanderChelotritonare added, the difference between LH (R4; unconstrained) and TH (R5) rises to 10 steps, that between LH and PH (R6) to 15; the TH also requires several more regains of lost bones than the LH.Casineria, in which we tentatively identify a postbranchial lamina, emerges rather far from amniote origins in a gephyrostegid-chroniosuchian grade. Bayesian inference (Analysis EB, settings as in R4) mostly agrees with R4. High posterior probabilities are found for Lissamphibia (1.00) and the LH (0.92); however, many branches remain weakly supported, and most are short, as expected from the small character sample. We discuss phylogeny, approaches to coding, methods of phylogenetics (Bayesian inference vs. equally weighted vs. reweighted parsimony), some character complexes (e.g. preaxial/postaxial polarity in limb development), and prospects for further improvement of this matrix. Even in its revised state, the matrix cannot provide a robust assessment of the phylogeny of early limbed vertebrates. Sufficient improvement will be laborious—but not difficult.

Reproducibility in phylogenetics: reevaluation of the largest published morphological data matrix for phylogenetic analysis of Paleozoic limbed vertebrates

The largest published phylogenetic analysis of early limbed vertebrates (Ruta M, Coates MI. 2007. Journal of Systematic Palaeontology 5:69–122) recovered e.g. Seymouriamorpha, Diadectomorpha and (in some trees) Caudata as paraphyletic and found the “temnospondyl hypothesis” on the origin of Lissamphibia (TH) to be more parsimonious than the “lepospondyl hypothesis” (LH) – though only, as we show, by one step. We report thousands of misscored cells, most of them due to typographic and similar accidental errors. Further, some characters are duplicated; some have only one described state; for some, most taxa were scored after presumed relatives. Even continuous characters were unordered, the effects of ontogeny were not sufficiently taken into account, and data published after 2001 were mostly excluded. After these issues are improved – we document and justify all changes to the matrix –, but no characters are added, we find (Analysis R1) much longer trees with e.g. monophyletic Caudata, Diadectomorpha and (in some trees) Seymouriamorpha; Ichthyostega either crownward or rootward of Acanthostega; Anthracosauria either crownward or rootward of Temnospondyli; the LH is 9 steps shorter than the TH (R2; constrained) and 12 steps shorter the “polyphyly hypothesis” (PH – R3; constrained). Brachydectes (Lysorophia) is not found next to Lissamphibia; instead, the sister-group of Lissamphibia is a large clade that includes adelogyrinids, urocordylid “nectrideans” and aïstopods. Adding 56 OTUs to the original 102 increases the resolution. The added taxa range in completeness from complete articulated skeletons to an incomplete lower jaw. Even though the lissamphibian-like temnospondyls Gerobatrachus, Micropholis and Tungussogyrinus and the extremely peramorphic salamander Chelotriton are added, the difference between LH (R4) and TH (R5) rises to 10 steps, that between LH and PH (R6) to 15; the TH also requires several more regains of lost bones than the LH. Most bootstrap values are low, and plummet when taxa are added. Statistically, the TH (R2, R5) is not distinguishable from the LH or the PH; the LH (R1) and the PH (R3) may be distinguishable from each other under the original taxon sample at p ≥ 0.04. A test for the upper bound of the p value is not available. Bayesian inference (Analysis EB, same settings as R4) mostly agrees with R4. High posterior probabilities are found for Lissamphibia (1.00) and for the LH (0.92); however, many branches remain weakly supported, and most are short, as expected from the small character sample. We discuss phylogeny, approaches to coding, methods of phylogenetics (Bayesian inference vs. equally weighted vs. reweighted parsimony), some character complexes, and prospects for further improvement of this matrix. In its present state, even after our changes, the matrix cannot provide a robust assessment of the phylogeny of early limbed vertebrates; sufficient improvement, however, will be laborious but not difficult.

Reproducibility in phylogenetics: reevaluation of the largest published morphological data matrix for phylogenetic analysis of Paleozoic limbed vertebrates

The largest published phylogenetic analysis of early limbed vertebrates (Ruta M, Coates MI. 2007. Journal of Systematic Palaeontology 5:69–122) recovered e.g. Seymouriamorpha, Diadectomorpha and (in some trees) Caudata as paraphyletic and found the “temnospondyl hypothesis” on the origin of Lissamphibia (TH) to be more parsimonious than the “lepospondyl hypothesis” (LH) – though only, as we show, by one step. We report thousands of misscored cells, most of them due to typographic and similar accidental errors. Further, some characters are duplicated; some have only one described state; for some, most taxa were scored after presumed relatives. Even continuous characters were unordered, the effects of ontogeny were not sufficiently taken into account, and data published after 2001 were mostly excluded. After these issues are improved – we document and justify all changes to the matrix –, but no characters are added, we find (Analysis R1) much longer trees with e.g. monophyletic Caudata, Diadectomorpha and (in some trees) Seymouriamorpha; Ichthyostega either crownward or rootward of Acanthostega; Anthracosauria either crownward or rootward of Temnospondyli; the LH is 9 steps shorter than the TH (R2; constrained) and 12 steps shorter the “polyphyly hypothesis” (PH – R3; constrained). Brachydectes (Lysorophia) is not found next to Lissamphibia; instead, the sister-group of Lissamphibia is a large clade that includes adelogyrinids, urocordylid “nectrideans” and aïstopods. Adding 56 OTUs to the original 102 increases the resolution. The added taxa range in completeness from complete articulated skeletons to an incomplete lower jaw. Even though the lissamphibian-like temnospondyls Gerobatrachus, Micropholis and Tungussogyrinus and the extremely peramorphic salamander Chelotriton are added, the difference between LH (R4) and TH (R5) rises to 10 steps, that between LH and PH (R6) to 15; the TH also requires several more regains of lost bones than the LH. Most bootstrap values are low, and plummet when taxa are added. Statistically, the TH (R2, R5) is not distinguishable from the LH or the PH; the LH (R1) and the PH (R3) may be distinguishable from each other under the original taxon sample at p ≥ 0.04. A test for the upper bound of the p value is not available. Bayesian inference (Analysis EB, same settings as R4) mostly agrees with R4. High posterior probabilities are found for Lissamphibia (1.00) and for the LH (0.92); however, many branches remain weakly supported, and most are short, as expected from the small character sample. We discuss phylogeny, approaches to coding, methods of phylogenetics (Bayesian inference vs. equally weighted vs. reweighted parsimony), some character complexes, and prospects for further improvement of this matrix. In its present state, even after our changes, the matrix cannot provide a robust assessment of the phylogeny of early limbed vertebrates; sufficient improvement, however, will be laborious but not difficult.

The Endocranial Cavity of Oviraptorosaur Dinosaurs and the Increasingly Complex, Deep History of the Avian Brain

Unraveling the origins of the character complexes diagnosing major crown clades is one of the greatest challenges in evolutionary biology. These origination events tend to optimize along extraordinarily long stem lineages where the comparative biology of extant lineages is relatively weak in its heuristic power. Here we add to a growing paleontological literature on the evolutionary origins of the modern avi an brain by describing the endocranial casts of two oviraptorosaur dinosaurs, Citipati osmolskae and Khaan mckennai. These fossil data confirm the antiquity of several avian features, including the expanded cerebrum. They also extend our appreciation of both the inherent variability in the brain-skull relationship along the avian stem and the dynamic nature of these crown characters in the earliest history of their expression.

Reevaluation of the largest published morphological data matrix for phylogenetic analysis of Paleozoic limbed vertebrates

The largest published data matrix for phylogenetic analysis of Paleozoic limbed vertebrates (Ruta M, Coates MI. 2007. Journal of Systematic Palaeontology 5:69–122) supported variously controversial hypotheses; e.g., it recovered Seymouriamorpha, Diadectomorpha and (in some trees) Caudata as paraphyletic and found the “temnospondyl hypothesis” on the origin of Lissamphibia (TH) to be more parsimonious than the “lepospondyl hypothesis” (LH) – though only, as we show, by one step. We report thousands of suboptimal scores due to typographic and similar errors and to questionable coding decisions: logically linked (redundant) characters, others with only one described state, even characters for which most taxa were scored after presumed relatives. Even continuous characters were unordered, the effects of ontogeny were not sufficiently taken into account, and data published after 2001 were mostly excluded. After these issues are improved – we document and justify all changes to the matrix –, but no characters are removed or added, we find (Analysis R1) much longer trees with e.g. monophyletic Caudata, Diadectomorpha and (in some trees) Seymouriamorpha; Ichthyostega rootward of Acanthostega; Anthracosauria rootward of Temnospondyli which includes Caerorhachis; the LH is 9 steps shorter than the TH (R2; constrained) and 12 steps shorter the “polyphyly hypothesis” (PH – R3; constrained). We then added 48 OTUs to the original 102. This destabilizes some parts of the tree, e.g. the positions of Anthracosauria, Temnospondyli and Caerorhachis. Yet, many added taxa have well-resolved positions, ranging from the well known Chroniosaurus (Chroniosuchia), which lies just crownward of Temnospondyli and Gephyrostegidae, to isolated lower jaws. Even though Gerobatrachus, Micropholis and Tungussogyrinus and the extremely peramorphic salamander Chelotriton are added, the difference between LH (R4) and TH (R5) rises to 12 steps, that between LH and PH (R6) to 17 steps; the TH also requires several more regains of lost bones than the LH. Brachydectes (Lysorophia) is not found next to Lissamphibia. We duplicated all analyses after coding losses of bones as irreversible. The impact on the results is modest. Anthracosauria is always rootward of Temnospondyli. With 102 OTUs, the LH (R7) is 10 steps shorter than the TH (R8) and 11 steps shorter than the PH (R9); with 150, the LH (R10) is 14 steps shorter than the TH (R12) – and 13 steps shorter than the PH (R11). Bootstrap values are mostly low, and plummet when taxa are added. Statistically, the TH (R2, R5, R8, R12) is not distinguishable from the LH or the PH, but the LH (R1, R4, R7, 53 R10) and the PH (R3, R6, R9, R11) may be distinguishable from each other under both taxon samples and both reversibility settings. A reliable test is not available. We discuss the relationships of certain taxa, approaches to coding, some character complexes, and prospects for further improvement of this matrix.

Reevaluation of the largest published morphological data matrix for phylogenetic analysis of Paleozoic limbed vertebrates

The largest data matrix for phylogeny of early limbed vertebrates (Ruta M, Coates MI. 2007. J. Syst. Palaeont. 5:69–122) has supported controversial hypotheses; e.g., it has recovered Seymouriamorpha, Diadectomorpha and (in some trees) Caudata as paraphyletic and found the “temnospondyl hypothesis” on the origin of Lissamphibia (TH) to be one step more parsimonious than the “lepospondyl hypothesis” (LH). Scrutiny of the matrix reveals thousands of suboptimal scores (many clearly due to typographic and similar errors) as well as logically linked (redundant) characters, characters with only one described state, and even cases where taxa were scored after presumed relatives. Moreover, all characters – even obviously continuous ones – were unordered, effects of ontogeny were not sufficiently taken into account, and the authors mostly excluded data published after 2001, even their own. Our revised version – we document and justify all changes – yields much longer trees with a different topology, e.g. monophyletic Caudata, Diadectomorpha and (sometimes) Seymouriamorpha, Ichthyostega more rootward than Acanthostega, Anthracosauria more rootward than Temnospondyli, and the LH, which is 10 steps more parsimonious than the TH and 15 more than the “polyphyly hypothesis” (PH). Bootstrap values, though, are low, and few of the topologies are statistically distinguishable. For another set of analyses, we added 48 OTUs to the original 102. This destabilizes parts of the tree, e.g. the relationships of Anthracosauria and Temnospondyli. However, many of the added taxa have a fully resolved position or nearly so; this concerns the well-known Chroniosaurus (sister to a clade containing Solenodonsaurus, Seymouriamorpha, Diadectomorpha, Amniota and Amphibia), but also isolated lower-jaw material from the Devonian and Carboniferous. Despite the addition of Gerobatrachus, Micropholis and Tungussogyrinus and the extremely peramorphic salamander Chelotriton, the difference between LH and TH only shrinks to 9 steps, that between LH and PH to 13 steps. The “lepospondyl” Brachydectes is neither found as sister to Lissamphibia nor in the “microsaur” grade. Bootstrap values plummet, though, and all three hypotheses become statistically indistinguishable at p = 0.05. We then duplicated all analyses after coding all losses of bones as irreversible. Anthracosauria is then consistently placed more rootward than Temnospondyli; given the original taxon sample, the LH is 12 steps shorter than the “temnospondyl hypothesis” and 17 steps shorter than the PH, while the expanded taxon sample makes the LH 10 steps shorter than the TH and only 12 steps shorter than the PH. More robust results could likely be obtained by adding the many characters used in other analyses or discussed in the literature. We discuss phylogeny, approaches to coding, and certain character complexes, in particular the supposed middle ear of temnospondyls.