Neuroanatomy of the lumbosacral plexus in a highly diversified clade of South‐American lizards. Evolution and phylogenetic implications

Abstract

Only few published studies that describe the neuroanatomy of lizards. Here, we describe the neuroanatomy of several Iguanian species belonging to three families (species of Liolaemus and Phymaturus belonging to Liolaemidae, Tropidurus and Stenocercus as representatives of Tropiduridae, and Diplolaemus as a representative of Leiosauridae). Based on Sudan Black B staining and conventional dissections, the neuroanatomy of the lumbosacral region is described. Among the most outstanding results is the existence of a neuronal pattern of the lumbosacral plexus characteristic of Liolaemidae. In addition, it was found that in the genus Liolaemus the lumbosacral plexus is composed of five pairs of spinal nerves while in Phymaturus, Tropidurus, Stenocercus and Diplolaemus is composed from five to six pairs of spinal nerves (from pre-sacral, sacral, and caudal vertebrae). We find differences in the origin of the spinal nerves that constitute the plexus. In some cases, the pattern of nerves involved includes even the caudal vertebrae. Variation among taxa related to the zeugopodial innervation is described, and the homology of these nervous branches is discussed. Sexual differences were found in some species studied. Based on our results and available literature, we found three different patterns of innervation of the zeugopodium. The major contribution of this study is to provide a detailed description of lumbosacral plexus nerves pathways from their origins at the vertebral column to the muscles that they innervate.

Description of the neuroanatomy of the brachial plexus in South American lizards. Phylogenetic implications

“…Quipildor et al (2020) recovered potential synapomorphies for the clade formed by Leiosauridae + Liolaemidae, Liolaemidae, Liolaemus , Phymaturus , Tropidurus , Eulaemus , and the P. patagonicus group. The results presented by Quipildor et al (2020) show that the neuroanatomy and more specifically the anatomy of the lumbar plexus provide information that could help elucidate the phylogenetic relationships between the groups. Our mapping of the characters studied showed potential synapomorphies in the different groups.…”

“…The information obtained from the nerve plexuses has been little used for a phylogenetic analysis of the groups (Estes et al, 1988; Etheridge & de Queiroz, 1988; Frost & Etheridge, 1989; Gauthier et al, 2012; Quipildor et al, 2020). Renous–Lécuru, (1972), mentions the importance of the data obtained by neuroanatomical studies to reveal the phylogenetic relationships within the group of lizards.…”

“…More recently, Quipildor et al (2020) recognized a total of 52 characters from the lumbosacral plexus and its associated nerves in species of the families Leiosauridae, Liolaemidae, and Tropiduridae. Quipildor et al (2020) recovered potential synapomorphies for the clade formed by Leiosauridae + Liolaemidae, Liolaemidae, Liolaemus , Phymaturus , Tropidurus , Eulaemus , and the P. patagonicus group.…”

“…The most recent study about the NS is that of Quipildor et al (2020). Teh authors recognize 52 characters from the lumbosacral plexus and its associated nerves in species of the families Leiosauridae, Liolaemidae, and Tropiduridae.…”

“…Even though squamates exhibit great biodiversity and morphological variations, few studies describe the anatomy of the nervous plexuses (Table 1), more than half of which result from graduate or postgraduate theses, some yet to be published in scientific journals (Akita, 1992;Díaz, 1996;Jerez, 2007;Renous-Lécuru, 1972). Most of the studies on comparative anatomy in reptiles are mainly based on coloration, morphometry, musculature, and osteology (Lobo & Abdala, 2001;Marín & Hernando, 2016;Cánovas et al, 2006;Martins, 2016;Quipildor, 2019;Salica & Halloy, 2009;Vidal Alvarez, 2020; among others), and few on the NS (Akita, 1992;Arantes et al, 2017;Diaz, 1996;Filipski & Wilson, 1984, 1985, 1986Jerez, 2007;Mivart & Clarke, 1877;Quipildor et al, 2020;Renous-Lécuru, 2007;Wyneken, 2007). Mivart and Clarke (1877), described the lumbar plexus of many species of lizards, pointing out that in general the lumbar plexus can be formed by two or three roots.…”