Wiki: Condylarthra - upcScavenger

Condylarthra is an informal group – previously considered an order – of extinct , known primarily from the Paleocene and Eocene epochs. They are considered early, primitive ungulates and is now largely considered to be a wastebasket taxon, having served as a dumping ground for classifying ungulates which had not been clearly established as part of either Perissodactyla or Artiodactyla, being composed thus of several unrelated lineages.

Taxonomic history

Condylarthra always was a problematic group. When first described by , Phenacodontidae was the type and only family therein. , however, raised Condylarthra to an order and included a wide range of diverse placentals with generalized and postcranial skeletons. More recent researchers (i.e. post-WW2) have been more restrictive; either including only a limited number of taxa, or proposing that the term should be abandoned altogether. Due to their primitive characteristics condylarths have been considered ancestral to several ungulate orders, including the living Artiodactyla, Cetacea, Perissodactyla, Hyracoidea, Sirenia, and Proboscidea, as well as the extinct Desmostylia, Embrithopoda, Litopterna, Notoungulata, and Astrapotheria.

Kenneth D. Rose (2025). 9780801892219, Johns Hopkins University Press. ISBN 9780801892219

delimited condylarths as those having the following characters, but lacking the specializations present in more derived orders:

superior ramus of stapedial artery shifted to Petrosal bone or lost
mastoid foramen lost
Auditory bulla if present composed of ectotympanic
relatively bunodont teeth with low cusp relief
of lower molars shortened anteroposteriorly
large, posteriorly projecting hypoconulid on M₃ (lower third molar)
head of Talus bone is short and robust

Evolutionary history

The disappearance of the non-avian dinosaurs opened up an ecological niche for large mammalian . Some condylarths evolved to fill the niche, while others remained insectivorous. This may explain, in part, the tremendous evolutionary radiation of the condylarths that we can observe throughout the Paleocene, resulting in the different groups of (or " mammals") that form the dominant herbivores in most Cenozoic animal communities on land, except on the island continent of Australia.

Among recent mammals, Paenungulata (, , and sirenia), Perissodactyla (, , and ), Artiodactyla (, deer, antelope, , , hippopotamus, and their relatives), Cetacea (), and Tubulidentata () are traditionally regarded as members of the Euungulata. Besides these, several extinct animals also belong to this group, especially the endemic orders of ungulates, (Meridiungulata). Although many ungulates have hooves, this feature does not define the Euungulata. Indeed, some condylarths had small hooves on their feet, but the most primitive forms are .

Recent molecular and DNA research has reorganised the picture of mammalian evolution. Paenungulates and tubulidentates are seen as , and no longer seen as closely related to the perissodactyls, artiodactyls, and cetaceans, implying that hooves were acquired independently (i.e. were analogous) by at least two different mammalian lineages, once in the Afrotheria and once in the Laurasiatheria. Condylarthra itself, therefore, is polyphyletic: the several condylarth groups are not closely related to each other at all. Indeed, Condylarthra is sometimes regarded as a 'wastebasket' taxon. True relationships remain in many cases unresolved.

In addition to meridiungulates and living ungulates, a condylarthran ancestry has been proposed for several other extinct groups of mammals, including Mesonychia and Dinocerata.

Taxonomy