Asteriornis maastrichtensis Field &amp; Benito &amp; Chen &amp; Jagt &amp; Ksepka 2020, gen.et sp.nov.
Creators: name: Field, Daniel J.
name: Benito, Juan
name: Chen, Albert
name: Jagt, John W. M.
name: Ksepka, Daniel T.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Asteriornis
Asteriornis maastrichtensis

description: <i>Asteriornis maastrichtensis</i> <b>gen.et sp.nov.</b> <b>Remarks.We use Avialae to refer to theropods crownward of Dromaeosauridae and Troodontidae. Neornithes is equivalent to the bird crown</b> group (Aves sensu Gauthier,198623).Pangalloanserae defines the most inclusive clade including <i>Anser anser</i> <b>and</b> <i>Gallus gallus</i> <b>but not</b> <i>Passer domesticus</i> <b>(that is,the galloanseran total group).Further phylogenetic definitions are presented in the Supplementary Information.</b> 1 Department of Earth Sciences,University of Cambridge,Cambridge, UK. 2 Department of Biology &amp; Biochemistry,Milner Centre for Evolution,University of Bath,Bath,UK. 3 Natuurhistorisch Museum Maastricht,Maastricht,The Netherlands. 4 Bruce Museum, Greenwich,CT,USA. <b>✉</b> e-mail:djf70@cam.ac.uk <b>Etymology.</b> <i>Asteriornis</i>, <b>from the name of the Titan goddess</b> <i>Asteria</i> <b>and the Greek</b> <i>ornis</i> <b>for bird.In Greek mythology Asteria is the goddess of falling stars and transforms herself into a quail—attributes that are reflected by both the impending Cretaceous–Palaeogene(K–Pg) asteroid impact and the galloanseran affinities of</b> <i>Asteriornis</i>. <b>The specific epithet</b> <i>maastrichtensis</i> <b>reflects the provenance of the holotype—the Maastricht Formation (the type locality of the Late Cretaceous Maastrichtian stage).</b> <b>Holotype. Natuurhistorisch Museum Maastricht (NHMM) 2013 008, a nearly complete, articulated skull including mandibles and associated postcranial remains preserved in four blocks (Fig. 1, Extended Data Figs.1–7;see Supplementary Information for videos,character information,measurements,additional description and discussion). Preserved elements include the premaxillae,maxillae,nasals,frontals, laterosphenoid,basisphenoid,mesethmoid, left quadrate,left jugal, right palatine and lower jaws.Associated postcranial elements include incomplete femora,tibiotarsi,tarsometatarsus and radius.</b> <b>Locality and age. CBR-Romontbos Quarry,Eben-Emael,Liège, Belgium. Valkenburg Member(66.8–66.7million years old <b> 24</b> <b>), Maastricht Formation,Late Maastrichtian,Cretaceous.Additional details regarding the locality and stratigraphic setting are presented in the Supplementary Information.</b> </b> <b>Diagnosis.</b> <i>Asteriornis</i> <b>is unique among known taxa in exhibiting caudally pointed nasals that overlie the frontals and meet at the midline</b> <b>of the skull,and a slightly rounded, unhooked tip of the premaxilla. Additional character combinations from phylogenetic analyses that dif- ferentiate</b> <i>Asteriornis</i> <b>are presented in the Supplementary Information.</b> Description <i>Asteriornis maastrichtensis</i> <b>is a small pan-galloanseran, with an estimated mean body mass from hindlimb scaling regressions of 394 g (around the 21st percentile among extant Galloanserae</b> <b> 25</b> <b>; Extended Data Fig.8).Complete measurements of NHMM 2013 008 are provided in the Supplementary Information.</b> <b>Most major cranial components are in their original anatomical positions.The general appearance of the premaxillary beak resembles that of extant Galliformes,particularly in its gently down-curved tip and delicate construction,with no ossified joints among the rostral components</b> <b> 26</b> <b>. The contralateral frontal processes of the premaxillae are unfused along their length,and the premaxillae and nasals are unfused at both their tomial and narial contacts. The beak tip is unhooked, which distinguishes</b> <i>Asteriornis</i> <b>from most Galloanserae except certain Anatidae and Presbyornithidae.</b> <b>The skull lacks a distinct nasofrontal hinge.As such,the architecture of this region more closely resembles that of extant Galliformes than Anseriformes.At the midpoint of the orbits the frontals are constricted,yielding an hourglass-shaped cranial roof with wider rostral and caudal extremities. Indorsolateralview,therightpostorbitalprocesssweepsstronglyventrally beforedeflectingrostrallytodefinepartoftheventralmarginoftheorbit.</b> <b>The left quadrate is well-preserved in three dimensions and is generally similar to the quadrate of the fossil pan-anseriform</b> <i>Presbyornis</i> <b> 27</b> <b>(Fig. 2, Extended Data Fig. 4). The prootic and squamosal heads are divided by a well-developed incisure,as in almost all Neognathae;this contrasts with the condition in crownward stem birds such as</b> <i>Ichthyornis</i>, <b>in which the division between these condyles is poorly marked,and Palaeognathae,in which the condyles merge into a single head.Two pneumatic foramina pierce the quadrate:the foramen pneumaticum rostromediale and the foramen pneumaticum basiorbitale.A tuberculum subcapitulare is moderately developed on the lateral face of the otic process.This characteristic has been considered a derived feature of Galloanserae</b> <b> 27</b> <b>; however,it is present in many Neoaves,and given its absence in Palaeognathae and</b> <i>Ichthyornis</i> <b>it might instead represent a synapomorphy of Neognathae.The cotyla quadratojugalis of the quadrate is fairly deep,with a complete,un-notched rim.The pterygoid articulation is more widely separated dorsally from the mandibular condyle than in most extant Galloanserae,and is very similar to that of</b> <i>Presbyornis</i>. <b>As in all known Galloanserae,the mandible of</b> <i>Asteriornis</i> <b>exhibits two cotylae for articulation with the bicondylar quadrate and a bladelike retroarticular process.This process is strongly hooked,and in its shape and proportions bears a strong resemblance to the condition in the pan-anseriform</b> <i>Anatalavis oxfordi</i> <b>(Fig. 1d, Extended Data Fig. 5). An elongate,slightly dorsally oriented processus medialis is preserved on the right jaw,as in all Galloanserae.</b> <b>The left distal femur is well-preserved,exhibiting a medial condyle with a bluntly angular profile between the articular surface of the condyle and its cranial margin. A detailed anatomical description of the skull and postcranium is provided in the Supplementary Information.</b>
description: Published as part of <i>Field, Daniel J., Benito, Juan, Chen, Albert, Jagt, John W. M. &amp; Ksepka, Daniel T., 2020, Late Cretaceous neornithine from Europe illuminates the origins of crown birds, pp. 397-414 in Nature 579</i> on pages 397-399, DOI: 10.1038/s41586-020-2096-0, http://zenodo.org/record/3716350
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