Females of many squamates maintain viable sperm in their reproductive tract after insemination. This 'female sperm storage' (FSS), has several advantages and clear implications for squamate evolution by dramatically influencing life histories, mating systems, and sexual selection and conflict. In this chapter, we summarize the literature on the anatomy of FSS and reconstruct the evolution of sperm-storage location in squamate reptiles. Our major aim is to provide insights into the evolution of FSS in squamates, with a particular focus on the origin and early evolution of snakes. Various lizard lineages store sperm exclusively in crypts or tubules in the posterior oviduct. Most ‘basal’ lizards (gekkotans) and all ‘basal’ snakes (scolecophidians) studied thus far store sperm in tubules in the anterior oviduct. A few gekkotans and most alethniophidian snake studied store (or potentially store) sperm in both oviductal regions. Some snakes apparently have evolved morphological adaptations to hold sperm in the posterior oviduct. Based on ancestral state reconstructions, we elaborate a scenario for the evolution of FSS in snakes.

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.

Oral glands underwent substantial modification during the origin and diversification of snakes. Oral glands have provided rich data for snake systematics, and for informing evolutionary scenarios about the adaptive radiation of snake feeding. However, sampling has been patchy, and many questions remain about gland homology, function and evolution. This chapter addresses labial (supra- and infralabial), temporomandibular, rictal, sublingual, premaxillary, accessory and dental (= venom and Duvernoy’s) glands. We review and synthesize developments and data and present new histological sections and high-resolution tomography of some snakes and lizards, providing descriptions and illustrations of oral glands and associated structures. We comment on labial and dental glands of some toxicoferan and non-toxicoferan lizards, and report the first observation of a possible infralabial gland in a dibamian lizard. There are insufficient data to resolve all outstanding questions about gland homology across lizards and snakes, but the ancestral snake possibly had rictal and lacked dental (venom) glands, the latter perhaps evolving only within colubroidean caenophidians.