A further attempt to detect discontinuity surrounding the Equidae, using a new dataset.
Paul Garner (Biblical Creation Trust)
The bottom line:
Baraminological studies have so far failed to establish strong evidence of discontinuity surrounding the Equidae, either because an outgroup was not included in the analysis or because the datasets were not sufficiently holistic. This study made another attempt to resolve this question using a new dataset, but the results remained inconclusive.
This study involved baraminic distance correlation (BDC) analyses based on Danilo et al. (2013), consisting of 26 taxa and 72 characters (six cranial and 66 dental). This dataset included 24 characters for these taxa that were additional to those in already published datasets (Hooker 1994, Froehlich 2002, Badiola et al. 2005). Two of the ingroup taxa were equids; the rest were palaeotheres and other non-equid equoids. The outgroup taxon was the tapiromorph Cardiolophus radinskyi.
In the first analysis, all characters with less than 75% relevance were eliminated, leaving 57 characters; all the cranial characters were excluded. Three clusters of taxa were discerned: (1) Five palaeotheres: Anchilophus dumasi + Paranchilophus remyi + Lophiotherium cervulum + Palaeotherium magnum + Plagiolophus minor ; (2) Most other taxa, including the equids and the outgroup taxon; (3) Four species of the genus Pachynolophus: Pachy. bretovensis + Pachy. garimondi + Pachy. lavocati + Pachy. zambranensis. The first group showed significant negative correlations with the second group; the third group showed no positive correlations with members of the first group but some positive and some negative correlations with members of the second group. Eurohippus parvulus was neither positively nor negatively correlated with any other taxon.
The analysis was re-run, with the first discontinuity-bounded group of five taxa excluded from the dataset. The aim was to see whether this would help to resolve any discontinuities among the remaining taxa. All characters with less than 75% relevance were excluded, leaving 21 taxa and 54 characters. Again, all six cranial characters were excluded. The outgroup taxon was neither positively nor negatively correlated with any other taxon. Eurohippus parvulus was negatively correlated with Xenicohippus osborni, but otherwise not positively or negatively correlated with any other taxon. Excluding these taxa, two clusters were evident: (1) Four species of the genus Pachynolophus: Pachy. bretovensis + Pachy. garimondi + Pachy. lavocati + Pachy. zambranensis. (2) All remaining taxa, including the equids. Where statistically significant correlations were evident between the two groups, most were negative; however species of Pachynolophus occurred in both groups and some were positively correlated with one another. Perhaps notably, the equid, Pliolophus vulpiceps, was negatively correlated with all four members of the Pachynolophus cluster.
Danilo et al. (2013, p.205) pointed out that many of the species in their dataset were defined with only one tooth row or some isolated teeth. Thus, despite the inclusion of additional characters, the available datasets were still very non-holistic and it was inappropriate to draw strong conclusions. However, from the second analysis a weak conclusion was drawn of morphological discontinuity between the group that includes the equids and the group comprising Pachy. bretovensis + Pachy. garimondi + Pachy. lavocati + Pachy. zambranensis.
The results of this study were presented at the Origins 2016 conference (Garner 2016).
Badiola, A., X. Pereda-Suberbiola, and M.A. Cuesta. 2005. Una nueva especie de Pachynolophus (Mammalia, Perissodactyla) de Zambrana (Álava, Región Vasco-Cantábrica). Análisis filogenético de Pachynolophus y primera cita en el Eoceno superior de la Península Ibérica. Geobios 38:1-16.
Danilo, L., J.A. Remy, M. Vianey-Liaud, B. Marandat, J. Sudre, J., and F. Lihoreau. 2013. A new Eocene locality in southern France sheds light on the basal radiation of Palaeotheriidae (Mammalia, Perissodactyla, Equoidea). Journal of Vertebrate Paleontology 33:195-215.
Froehlich, D.J. 2002. Quo vadis eohippus? The systematics and taxonomy of the early Eocene equids (Perissodactyla). Zoological Journal of the Linnean Society 134:141-256.
Garner, P. 2016. A further attempt to detect discontinuity surrounding the Equidae, using a new dataset. Journal of Creation Theology and Science Series B: Life Sciences 6:60. See page 2 of PDF file.
Hooker, J.J. 1994. The beginning of the equoid radiation. Zoological Journal of the Linnean Society 112:29-63.