SVP 2021 abstracts – 12: Passerines

Steel et al. 2021 discuss the bird clade, Passeriformes
“The major crown bird subclade Passeriformes (= Passerines) comprises >6,000 extant species, making up over half of extant avian diversity.”

Maybe more. Most bird cladograms don’t include moas, chickens and parrots in this clade. Traditionally crows are considered Passeriformes. In the large reptile tree (LRT, 1991+ taxa) crows (Corvus) are basal members of this clade and Passer, the sparrow, is a derived, phylogenetically miniaturized chicken, basal to hoatzins, moas and parrots.

According to Wikipedia:
Passerines are divided into three suborders: Acanthisitti (New Zealand wrens), Tyranni (suboscines), and Passeri (oscines). The passerines contain several groups of brood parasites such as the viduas, cuckoo-finches, and the cowbirds. Most passerines are omnivorous, while the shrikes are carnivorous.

Steel et al. 2021 continue:
“Recent work provides a robust phylogenomic framework for extant passerine diversity, yet limited work has targeted passerine comparative anatomy on a broad phylogenetic scale.

The LRT is one of those ‘limited works’ that employs comparative anatomy on a broad phylogenetic scale. Genomic studies cannot be trusted in deep time studies.

This has contributed to a long-standing misconception that passerines exhibit morphologically “uniform” skeletons, which may have dissuaded workers from pursuing large-scale comparative osteological studies of passerines.”

Interesting, Wish I knew which taxa they nested within Passeriformes because the LRT usually breaks all prior taxonomic conventions. I’m going to guess that parrots and moas were not included because they never are included with sparrows and chickens.

“As such, many components of the passerine skeleton are understudied, and existing morphological matrices tend to identify relatively few phylogenetically informative characters for each skeletal component.

What is ‘relatively few’? And what is enough to lump and separate all included taxa? The authors don’t say, but at least they are studying traits.

“This has hindered interpretation of the passerine fossil record, as many isolated fossils of passerine bones remain unassigned beyond the ordinal or subordinal level. Isolated carpometacarpi are preserved relatively frequently, with numerous passerine carpometacarpi known from the Cenozoic.

“Here, we present a detailed analysis of the passerine carpometacarpus, towards the goal of improving comparative morphological knowledge across Passeriformes. We identify morphological synapomorphies for major passerine subclades, sampling 100 taxa distributed across extant passerine diversity.”

When an analysis keeps a focus on just the carpometatarsus
prior to establishing a valid cladogram that runs the risk of omission and convergence.

“Our approach marshalled both published characters and a substantial amount of previously undescribed anatomical variation, resulting in >50 phylogenetically informative characters that were optimized across a robust phylogenomic scaffold derived from recent studies. Our results show high levels of homoplasy within the passerine carpometacarpus, and that several frequently quoted “diagnostic” characters for particular clades exhibit previously unrecognized homoplasy.”

Sounds like the authors are being rather careful. Glad to see they are working with a last common ancestor method, rather than depending on ‘diagnostic’ characters.

“Despite this, we identify numerous diagnostic character combinations for key passerine clades. The character matrix from this study will aid in future diagnoses of isolated passerine
carpometacarpus fossils, enabling insight into when and where representatives of major passerine clades first appear in the fossil record. This work provides a starting
point for large-scale comparative analyses of the passerine skeleton, and reveals a substantial degree of previously unrecognized morphological variation among Passeriformes.”

Did the authors include moas? Parrots? Woodpeckers? Hoatzins? If not, it’s time to do so.

References
Steell E, Nguyen J, Benson RB and Field DJ 2021. Comparative morphology of the passeine carpometacarpus: implications for interpreting the fossil record of crown passeriformes. Journal of Vertebrate Paleontology abstracts.

wiki/Passerine