Book contents
- The Origin and Early Evolutionary History of Snakes
- The Systematics Association Special Volume Series
- The Origin and Early Evolutionary History of Snakes
- Copyright page
- Dedication
- Contents
- Contributors
- Preface
- 1 Introduction
- Part I The Squamate and Snake Fossil Record
- Part II Palaeontology and the Marine-Origin Hypothesis
- Part III Genomic Perspectives
- Part IV Neurobiological Perspectives
- Part V Anatomical and Functional Morphological Perspectives
- 16 Diversity and Evolution of Squamate Hemipenes
- 17 The Evolution of Sperm-Storage Location in Squamata with Particular Reference to Snakes
- 18 An Overview of the Morphology of Oral Glands in Snakes
- 19 Macrostomy, Macrophagy, and Snake Phylogeny
- Index
- Series page
- References
16 - Diversity and Evolution of Squamate Hemipenes
An Overview with Particular Reference to the Origin and Early History of Snakes
from Part V - Anatomical and Functional Morphological Perspectives
Published online by Cambridge University Press: 30 July 2022
- The Origin and Early Evolutionary History of Snakes
- The Systematics Association Special Volume Series
- The Origin and Early Evolutionary History of Snakes
- Copyright page
- Dedication
- Contents
- Contributors
- Preface
- 1 Introduction
- Part I The Squamate and Snake Fossil Record
- Part II Palaeontology and the Marine-Origin Hypothesis
- Part III Genomic Perspectives
- Part IV Neurobiological Perspectives
- Part V Anatomical and Functional Morphological Perspectives
- 16 Diversity and Evolution of Squamate Hemipenes
- 17 The Evolution of Sperm-Storage Location in Squamata with Particular Reference to Snakes
- 18 An Overview of the Morphology of Oral Glands in Snakes
- 19 Macrostomy, Macrophagy, and Snake Phylogeny
- Index
- Series page
- References
Summary
Squamate hemipenes have yielded much systematic data, but there have been few, if any, attempts to infer changes across the lizard–snake transition. We assess external morphology of hemipenes of major extant squamate lineages. Summarizing information across Squamata from mostly published data is challenging because of (i) patchy coverage, (ii) uncertainty as to whether described organs are fully everted or inflated, (iii) interpreting mixed text, photographs and drawings, (iv) non-standardized terminology, (v) shifting views of squamate phylogeny. However, we provide suggestions towards a unified terminology for hemipenial morphology, and score 24 lineages for 10 traits. We infer likely ancestral states as follows. (1) Ancestral toxicoferan: slightly bilobed hemipenis; simple, flared sulcus spermaticus; lack of spines; possibly flounce-like transverse flanges on body. (2) Ancestral snake: simple, flared sulcus with closely spaced, symmetrical lips; lack of spines; lack of lobular calyces; possibly unilobed hemipenis. (3) Ancestral alethinophidian: moderately to deeply bilobed hemipenis; lobular flounces; lack of spines; centripetal, bifurcate sulcus reaching tips of lobes.
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- The Origin and Early Evolutionary History of Snakes , pp. 351 - 388Publisher: Cambridge University PressPrint publication year: 2022