Reappraisal on the Phylogenetic Relationships of the Enigmatic Flightless Bird (Brontornis burmeisteri) Moreno and Mercerat, 1891

Federico L. Agnolin

doi:10.3390/d13020090

Abstract

The fossil record of birds in South America is still very patchy. One of the most remarkable birds found in Miocene deposits from Patagonia is Brontornis burmeisteri Moreno and Mercerat, 1891. This giant flightless bird is known by multiple incomplete specimens that represent a few portions of the skeleton, mainly hindlimb bones. Since the XIX century, Brontornis was considered as belonging to or closely related to phorusrhacoid birds. In contrast to previous work, by the end of 2000 decade it was proposed that Brontornis belongs to Galloanserae. This proposal was recently contested based on a large dataset including both phorusrhacoids and galloanserine birds, that concluded Brontornis was nested among cariamiform birds, and probably belonged to phorusrhacoids. The aim of the present contribution is to re-evaluate the phylogenetic affinities of Brontornis. Based on modified previous datasets, it is concluded that Brontornis does belong to Galloanserae, and that it represents a member of a largely unknown radiation of giant graviportal birds from South America.

Highlights

The genus Brontornis was originally described by Moreno and Mercerat (1891) based on several specimens coming from Lower-Middle Miocene localities at Santa Cruz province, Patagonia, Argentina [1]
The genus Liornis was erected by Ameghino with the aim to include the single species L. floweri [2]
Brodkorb, in his renowned “Catalogue of fossil birds” [12] synonymized Liornis floweri to Brontornis burmeisteri without discussing this in detail, a point of view followed by Tonni [1] among other authors

Summary

Introduction

The genus Brontornis was originally described by Moreno and Mercerat (1891) based on several specimens coming from Lower-Middle Miocene localities at Santa Cruz province, Patagonia, Argentina [1]. Moreno and Mercerat [3] include Brontornis on its own family Brontornithidae in the Order Stereornithes (this later included several genera known as phorusrhacoids) In their concept, the Stereornithes were carinate birds with a shared combination of characters between anseriformes, coconiiforms (Herodiones therein), and accipitriforms, probably “intermediate” between Anatidae and Cathartidae. Ameghino considered the Stereornithes as belonging to Ratitae, and included Brontornis among phorusrhacids, a criterion was followed by most authors until Dolgopol de Sáez [10] She revalidated the Brontornithidae (as Brontorniidae) and based on morphological grounds coined the Order Brontornithes to separate them from remaining phorusrhacoids (encompassed by her in the Order Stereornithes). Subsequent authors followed Moreno and Mercerat and Ameghino views and considered Brontornis and kin as belonging to a different family or subfamily of phorusrhacoid birds [1,12,13,14], without regard of the distinctive anatomical features cited by Dolgopol de Sáez and Kraglievich

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Conclusion