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1. Craniofacial morphology of Adalatherium hui (Mammalia, Gondwanatheria) from the Late Cretaceous of Madagascar

   https://doi.org/https://doi.org/10.1080/02724634.2020.1808665  

   Krause, D.W. ; Hoffmann, S. ; Rossie, J.B. ; Hu, Y. ; Wible, John R. ; Rougier, G.W. ; Kirk, E.C. ; Groenke, J.R. ( December 2020 , Journal of vertebrate paleontology)

   null (Ed.)

   The cranium of Adalatherium hui, as represented in the holotype and only specimen (UA 9030), is only the second known for any gondwanatherian mammal, the other being that of the sudamericid Vintana sertichi. Both Adalatherium and Vintana were recovered from the Upper Cretaceous (Maastrichtian) Maevarano Formation of northwestern Madagascar. UA 9030 is the most complete specimen of a gondwanatherian yet known and includes, in addition to the cranium, both lower jaws and a complete postcranial skeleton. Aside from Adalatherium and Vintana, gondwanatherians are otherwise represented only by isolated teeth and lower jaw fragments, belonging to eight monotypic genera from Late Cretaceous and Paleogene horizons of Madagascar, the Indian subcontinent, Africa, South America, and the Antarctic Peninsula. Although the anterior part of the cranium is very well preserved in UA 9030, the posterior part is not. Nonetheless, comparable parts of the crania of Adalatherium and Vintana indicate some level of common ancestry through possession of several synapomorphies, primarily related to the bony composition, articular relationships, and features of the snout region. Overprinted on this shared morphology are a host of autapomorphic features in each genus, some unique among mammaliaforms and some convergent upon therian mammals. The cranium of Adalatherium is compared with the crania of other mammaliamorphs, particularly those of allotherians or purported allotherians (i.e., haramiyidans, euharamiyidans, multituberculates, Cifelliodon, and Megaconus). Particular emphasis is placed on several recently described forms: the enigmatic Cifelliodon from the Early Cretaceous of Utah and several new taxa of euharamiyidans from the Late Jurassic of China. 

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2. Late Cretaceous neornithine from Europe illuminates the origins of crown birds.

   https://doi.org/10.1038/s41586-020-2096-0  

   Field, Daniel J ; Benito, Juan ; Chen, A ; Jagt, John W. ; Ksepka, D. T. ( January 2020 , Nature)

   Our understanding of the earliest stages of crown bird evolution is hindered by an exceedingly sparse avian fossil record from the Mesozoic era. The most ancient phylogenetic divergences among crown birds are known to have occurred in the Cretaceous period but stem-lineage representatives of the deepest subclades of crown birds—Palaeognathae (ostriches and kin), Galloanserae (landfowl and waterfowl) and Neoaves (all other extant birds)—are unknown from the Mesozoic era. As a result, key questions related to the ecology, biogeography and divergence times of ancestral crown birds remain unanswered. Here we report a new Mesozoic fossil that occupies a position close to the last common ancestor of Galloanserae and fills a key phylogenetic gap in the early evolutionary history of crown birds. Asteriornis maastrichtensis, gen. et sp. nov., from the Maastrichtian age of Belgium (66.8–66.7 million years ago), is represented by a nearly complete, three-dimensionally preserved skull and associated postcranial elements. The fossil represents one of the only well-supported crown birds from the Mesozoic era, and is the first Mesozoic crown bird with well-represented cranial remains. Asteriornis maastrichtensis exhibits a previously undocumented combination of galliform (landfowl)-like and anseriform (waterfowl)-like features, and its presence alongside a previously reported Ichthyornis-like taxon from the same locality provides direct evidence of the co-occurrence of crown birds and avialan stem birds. Its occurrence in the Northern Hemisphere challenges biogeographical hypotheses of a Gondwanan origin of crown birds, and its relatively small size and possible littoral ecology may corroborate proposed ecological filters that influenced the persistence of crown birds through the end-Cretaceous mass extinction. 

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3. Evolution and biogeography of acidocerine water scavenger beetles (Coleoptera: Hydrophilidae) shaped by Gondwanan vicariance and Cenozoic isolation of South America

   https://doi.org/10.1111/syen.12467  

   Short, Andrew Edward Z. ; Girón, Jennifer C. ; Toussaint, Emmanuel F. A. ( January 2021 , Systematic Entomology)

   The water scavenger beetle subfamily Acidocerinae is a cosmopolitan, ecologically diverse lineage with more than 500 described species whose morphology and classification are poorly understood. We present the first phylogenetic analyses of the subfamily inferred from five loci (18S, 28S, H3, CAD, COI). We used secondary calibrations to estimate divergence times and employ this phylogeny to revise the classification and examine the historical biogeography of this lineage. Most genera are resolved as reciprocally monophyletic, with several exceptions:Horelophopsissyn. n.is recovered as a derived lineage of and placed in synonymy withAgraphydrus. The large genusHelochares, as well as its primary constituent subgeneraHelochares(s. str.) andHydrobaticusare found to be polyphyletic.Batocharesstat. n.andSindolusstat. rev.are elevated from subgenera ofHelocharesto generic rank.Crephelocharesstat. rev.is removed from synonymy withChasmogenus. We found that the crown Acidocerinae date to the mid‐Jurassic in South America + Africa (West Gondwana). South America and Africa remain important areas of endemism throughout the evolution of the lineage and are resolved either individually or in combination as the ancestral area for all but one clade that is older than 90 million years ago. Six of the seven lineages occurring in South America diverged more than 100 million years ago and are endemic to the region, suggesting the Neotropical acidocerine fauna became isolated following the breakup of West Gondwana. Conversely, lineages found on other Gondwanan fragments (India, Madagascar, Australia) are comparatively young and derived, with all being Cenozoic in age. The few taxa that occur in North America today are all the result of recent Cenozoic dispersal from South America, although North America may have played an important role as an ancestral area in the Mesozoic.

    

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4. A comprehensive meta-phylogeny of all non-mammalian synapsids: new tool for studies of macroevolution in the forerunners of mammals

   Hellert, Spencer ; Angielczyk, Kenneth D. ; Lloyd, Graeme ; Kammerer, Christian ; Grossnickle, David ( October 2022 , Journal of vertebrate paleontology)

   A large phylogenetic tree is a critical component of comparative analyses that examine broad macroevolutionary patterns, such as the tempo and mode of evolution or morphological disparity through time. However, the sample of species included in published phylogenies rarely aligns with the species that researchers wish to examine in comparative analyses. For instance, early synapsid phylogenies often focus on specific subclades, such as pelycosaurs or anomodonts, rather than broadly encompassing all known synapsid lineages, thus hindering analyses that require detailed sampling across synapsid lineages. To address this issue, we generated a time-calibrated meta-phylogeny (‘metatree’) of synapsid species from the Carboniferous through the Eocene (305–34 Ma). The metatree approach uses source character matrices (rather than source trees) and generates complete sets of most parsimonious trees, combining them rather than generating a single consensus tree. We incorporated 269 published morphological character matrices, which includes every non-mammaliaform synapsid character matrix that has ever been published (as of July 2021) and 57 mammaliaform-focused matrices. Due to evolving ideas of relationships and frequent matrix reuse, each of the matrices was weighted according to its publication year and its dependence on ‘parent’ matrices using an established metatree procedure. The metatree approach relies on XML metadata files that reconcile taxon names to valid Paleobiology Database taxa (PBDB). Because the metatree approach utilizes PBDB taxonomy, we vetted the PBDB information and made approximately 500 additions and corrections to taxon information. The resulting metatree includes 2,128 synapsid species, making it one of the largest fossil phylogenies ever produced. Approximately 1600 species are non-mammaliaform synapsids, and the remaining ~525 species are mammaliaforms, including many of the known Mesozoic and early Cenozoic mammaliaforms. The massive taxonomic and temporal breadth of the metatree make it broadly applicable to studies on synapsid macroevolution. The past decade has witnessed a resurgence of research on non-mammaliaform synapsids, and our new, comprehensive metatree provides a rigorous foundation for continuing work on macroevolutionary patterns and processes among the forerunners of mammals. 

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5. Lower jaw morphology of Adalatherium hui (Mammalia, Gondwanatheria) from the Late Cretaceous of Madagascar

   https://doi.org/https://doi.org/10.1080/02724634.2020.1805456  

   Krause, D.W. ; Hoffmann, S. ; Wible, John R. ; Rougier, G.W. ( December 2020 , Journal of vertebrate paleontology)

   null (Ed.)

   The lower jaw of the holotype of Adalatherium hui, from the Late Cretaceous of Madagascar, is the most complete yet known for a gondwanatherian mammal. It reveals for the first time the morphology of the character-rich ascending ramus of the dentary in a gondwanatherian. Each half of the lower jaw is composed of only one bone, the dentary, which is short and deep and houses only five teeth: an enlarged, procumbent incisor and four postcanine teeth. In comparable parts of its anatomy, the dentary of Adalatherium is strikingly similar to that of Sudamerica but differs slightly from that of Galulatherium (conformation anterior to first postcanine, mental foramen position), the only two other gondwanatherians represented by complete horizontal rami. Among other Mesozoic mammaliaform taxa, the dentary of Adalatherium is most similar to those of the largely Laurasian group Multituberculata, most notably in absence of postdentary trough and Meckelian sulcus; presence of short, deep dentary with sizable diastema and articulating with squamosal via mediolaterally narrow condyle that continues onto posterior surface (i.e., no distinct peduncle); possession of much reduced dentition; absence of angular process; possession of large pterygoid fossa and pterygoid shelf, ventral surface of which is flat; absence of coronoid bone; and possession of unfused mandibular symphysis. Most of these features are clearly derived and stand in stark contrast to the much more plesiomorphic morphology exhibited by the lower jaw of the haramiyaviid Haramiyavia. The lower jaws of euharamiyidans, although derived in their own right, are also relatively plesiomorphic. 

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