Amphisbaena mertensii (Squamata: Amphisbaenidae): Notes on natural history, distribution, and morphology Amphisbaena mertensii (Squamata: Amphisbaenidae): Notas sobre historia natural, distribución y morfología

Amphisbaena mertensii is a worm lizard species from South America. Because of its subterranean life-style, data on its biology are scarce. In this paper, we present the first record of A. mertensii as prey of a bird, the wood rail Aramides cajaneus . We also review the geographic range of this species, reporting it for 114 localities from west-central Brazil to northeastern Argentina. We update the range of precloacal pores in A. mertensii from 5–8 to 4–8


INTRODUCTION
Natural history observations are critical to the development of relevant hypotheses that can led to a new understanding of biodiversity and its evolution (Vitt 2013). Similarly, species geographic ranges are important to understand biogeographical patterns and processes, ultimately impacting conservation assessments (Morrone 2001, Hortal et al. 2015, Peixoto et al. 2020. Despite recent advances (e.g., Roll et al. 2017, Meiri 2018, adequate information on natural history and geographic range are still lacking for many species of squamate reptiles, particularly worm lizards (Amphisbaenia) (Andrade et al. 2006, Vitt and Caldwell 2014, Longrich et al. 2015, Colli et al. 2016), a group with over 200 known species worldwide Garcia 2019, Uetz et al. c2021). The paucity of information on the natural history and biogeography of amphisbaenians is in most part due to their fossorial habits, making them difficult to find. As result, this is one of the least known groups of Squamata (Vitt and Caldwell 2014, Costa and Garcia 2019, Navega-Gonçalves and Benites 2019).
frontalis Duméril, Bibron and Duméril, 1854 (Sazima and Abe 1991). It is also prey to mildly venomous species such as Phalotris mertensi (Hoge, 1955) (Duarte 2006) and even non-venomous species as Taeniophallus affinis (Günther, 1858) (Barbo et al. 2011) -but see Barbo and Sawaya (2008) for a correction of a predation record by Barbo and Marques (2003). Although birds are common predators of amphisbaenians (Schalk and Cove 2018), they have not been recorded preying on A. mertensii. In this work, we present the first evidence of A. mertensii as prey of a bird, based on a field observation. Additionally, we review the species' geographic range, filling gaps from recent published maps (Colli et al. 2016, Corrêa and Meneses 2020). Finally, based on specimens housed in scientific collections, we add information on the morphology of A. mertensii.

Literature review on geographic distribution
To review published records on the geographic range of A. mertensii, we gathered information from the species redescription (Gans 1966), followed by a search using the words "Amphisbaena mertensii" OR "Amphisbaena mertensi" in Google Scholar database (https://scholar.google.com/) in October 2020. We checked all issues of the journals Check List, Herpetology Notes, and Herpetological Review for notes on geographic distribution and natural history. We did not consider data from unpublished dissertations, theses, and technical reports.

RESULTS AND DISCUSSION
The predation event of the bird Aramides cajaneus upon Amphisbaena mertensii (Fig. 1) happened at 10:30 a.m. on a rainy day. The predator was on a road at the edge of a forest fragment, holding the prey's head in its beak. With the approach of the observer, the bird abandoned its prey on the ground, still alive and fled. Aramides cajaneus occurs in aquatic and semi-aquatic environments from Costa Rica (Loaiza-Gómez 2017) south to Uruguay and northern Argentina (Marcondes and Silveira 2015), feeding on a variety of terrestrial and aquatic prey such as crabs, snails, arthropods, frogs, and lizards (Redondo andQuesada 2012, Hipólito andSazima 2016, Silva e Silva and Olmos 2016). Since Amphisbaena mertensii is a fossorial species, the bird likely captured it while the worm lizard was foraging at the surface (Moraes and Recchia 2011) or because its burrows were flooded by the constant rain, forcing the reptile to come to the surface (Hayes et al. 2015).
It is likely that the predation of A. cajaneus on A. mertensii was opportunistic, as reported in other interactions between birds and worm lizards (Zamprogno and Sazima 1993, Hayes et al. 2015, Assis and Costa 2020. Our review on the geographic range of Amphisbaena mertensii produced 183 records at 110 localities, from west-central Brazil to northeastern Argentina. Four new locations of occurrence were added through our analysis of specimens from scientific collections, plus the present predation record (Fig. 2; Supplement 1). The two most recent published maps of A. mertensii cited 57 (Corrêa and Meneses 2020) and 68 (Colli et al. 2016) locality records. Our localities represent twice and 1.6 times the number of records from these two maps. Corrêa and Meneses (2020) alleged that their record from Brasília, central Brazil, is the northernmost known record of A. mertensii, but they and (Chaco, Argentina) in the west. The species can be found from low to mid-elevations, up to about 1000 m above sea level (Fig. 2). Its broad range reflects its capacity to inhabit a great variety of soil types, from loose sand to fine clay (FAO et al. c2012), although its skull type is not among those most specialized for burrowing (Gans 1968). This suggests that individuals of A. mertensii inhabit shallower soil depths and may forage on the surface more frequently (Gans 1968). The broad geographic range of A. mertensii may also suggest a cryptic diversity (Sampaio et al. 2015, Salvi et al. 2018) that deserves further attention and was previously suggested by Gans (1966).
We also highlight some questions about the type locality of Amphisbaena mertensii. The holotype this species was collected by Karl Heinrich Mertens (1796-1830) during a circumnavigation expedition between 1826 and 1829 (Lütke 1835, Strauch 1881). Strauch (1881) states that Mertens likely collected the specimen at some point on the coast of South America. Gans (1966) restricted the type locality of A. mertensii to the state of São Paulo, southeastern Brazil, based on the morphological affinities of the holotype with specimens from that region. However, the corvette Seniavine, of which Mertens was the chief naturalist, left Russia in September 1826, reaching Rio de Janeiro on the southeastern Brazilian coast on 7 January 1827, departing to Argentina and Cape Horn later that month (Lütke 1835). Apparently the Seniavine did not dock at any locality with known records of Amphisbaena mertensii, which raises some questions: Did Mertens receive the holotype from another person who collected it, in São Paulo? Did Mertens collect the specimen in Rio de Janeiro, from which no other specimen of A. mertensii is known? Was there a labeling mistake and the holotype is not actually linked to the Seniavine expedition? Further investigation is needed to resolve this issue.
However, the number of precloacal pores (four) is outside the known range for this species, previously reported as five to eight, usually six (Gans 1966, Silveira et al. 2012). This is a rare condition that is noteworthy since the number of precloacal pores is a taxonomic character for amphisbaenians Alexander 1962, Vanzolini 2002a).
Basic data on natural history, geographic range, and morphology expand the understanding of patterns and processes related to life on Earth (Vitt 2013, Hortal et al. 2015, Feldman et al. 2016, Schalk and Cove 2018. This is especially necessary for fossorial taxa such as amphisbaenians (Böhm et al. 2013, Colli et al. 2016. By reporting a previously unknown predator for Amphisbaena mertensii, compiling updated information about its geographic range, and recording new morphological data, we help to expose some secrets of those underground reptiles.

AUTHOR'S CONTRIBUTION
CLA collected field work data, prepared images, and wrote the text; HCC examined specimens, gathered literature data, prepared the map, and wrote the text; LR gathered literature data and wrote the text; RNF reviewed the text.

CONFLICT OF INTEREST
The authors declare that they have no conflict of interests.