New data on the tarantula genus Chaetopelma Ausserer, 1871 are provided. A new species, Ch. persianum sp. nov., is described based on a single female specimen collected in northwestern Iran, which represents the easternmost record of the genus within its entire known range. Additionally, the correct publication date of Ch. olivaceum C.L. Koch, 1842 is discussed, and the known distribution records of all Chaetopelma species are mapped.

Middle East, Mygalomorphae, spiders, tarantulas, taxonomy

Theraphosidae Thorell, 1869 is the largest family of mygalomorph spiders, currently encompassing over 1,000 species in 162 genera (WSC 2023). The family also includes four species known from fossils, of which Ischnocolinopsis acutus Wunderlich, 1988 and Protertheraphosa spinipes Wunderlich, 2020 represent monotypic genera from Neogene and Cretaceous Dominican amber, respectively (Dunlop et al. 2020). Commonly known as “tarantulas,” the majority of theraphosids are found in tropical, subtropical, and desert regions (Jocqué and Dippenaar-Schoeman 2006).

In the Middle East, Theraphosidae is represented by only two genera: Chaetopelma Ausserer, 1871 and Ischnocolus Ausserer, 1871. Both genera were traditionally considered closely related and part of the subfamily Ischnocolinae Simon, 1892 (Smith 1990). Nesiergus Simon, 1903, a small genus endemic to the Seychelles, has also been considered as sister to Chaetopelma (Smith 1990; Guadanucci and Gallon 2008). These proposed relationships, however, have recently been refuted. In the integrative analysis of Korba et al. (2022), Chaetopelma was recovered as sister to the African subfamily Eumenophorinae Pocock, 1897, and Ischnocolus and Nesiergus formed a clade with all the remaining theraphosids.

Chaetopelma is a relatively small genus that currently comprises six species distributed in the eastern Mediterranean and the Middle East, and one species from Cameroon (WSC 2023). A detailed taxonomic history of the genus was provided by Guadanucci and Gallon (2008). Chaetopelma species are fossorial tarantulas, living in burrows or within silk-lined chambers constructed beneath large stones and boulders and in the exterior dry walls of old houses and wells (Smith 1990).

In this study, we describe a new species of Chaetopelma collected in northwestern Iran, which represents the easternmost locality for the genus and its first recorded occurrence in Iran. Additionally, we discuss the correct publication date of Ch. olivaceum and provide a distribution map of all currently known species of Chaetopelma.

Photographs of the preserved specimen were obtained using an Olympus Camedia E‐520 camera attached to an Olympus SZX16 stereomicroscope. Digital images of different focal planes were stacked with Helicon Focus v. 8.1.1. The receptacles were photographed and illustrated after digesting tissues off in a 10% KOH aqueous solution. Body measurements exclude the chelicerae and spinnerets. Leg segments were measured on the dorsal side. Measurements of palp and legs are listed as: total length (femur, patella, tibia, metatarsus [absent on the palp], tarsus). All measurements are given in millimetres. The map was prepared using SimpleMappr (Shorthouse 2010) and modified using Adobe Photoshop. The extent of occurrence of Ch. olivaceum was calculated using GeoCAT (Bachman and Moat 2012). The exact geographic coordinates are omitted to prevent easy access to these places, considering the booming illegal trade with tarantulas. If precise coordinates are required for research, it is recommended to contact the institution in which the specimens are deposited and request them.

Abbreviations: Eyes: ALE – anterior lateral eye, AME – anterior median eye, PLE – posterior lateral eye, PME – posterior median eye. Spination: Mt – metatarsus, pl – prolateral, rl – retrolateral, Ti – tibia, v – ventral. Spinnerets: PLS – posterior lateral spinneret, PMS – posterior median spinneret.

Depositories: NHM – Natural History Museum, London, UK (J. Beccaloni); ZMUT – Zoological Museum of the University of Turku, Finland (V. Vahtera).

A new species of Chaetopelma was described in this paper, representing the easternmost known locality of the genus and its first recorded occurrence in Iran. Currently, only two other species of Theraphosidae are known from this country, both belonging to Ischnocolus: I. vanandelae Montemor, West & Zamani, 2020, and I. jickelii L. Koch, 1875 (Montemor et al. 2020; Zamani et al. 2022).

Although Chaetopelma has undergone a comprehensive revision (Guadanucci and Gallon 2008), we believe that further investigation, particularly those employing integrative methods, would greatly benefit the taxonomy of the genus. One species in particular, Ch. olivaceum, exhibits one of the broadest ranges within the entire family, with an extent of occurrence of approximately 1,493,978 km² (Fig. 5). As such, there is a possibility that cryptic species might exist within its expansive range. Furthermore, Ch. olivaceum exhibits a disjunct distribution in Turkey, being known to occur in both the southern regions of the country and as far north as Istanbul in the northwest (Fig. 5). It is plausible that integrative studies, specifically those incorporating molecular data, could reveal a distinct species status for the latter population, which is geographically isolated from the rest of the recorded occurrences. Moreover, it is expected that conducting further collection efforts in lesser-sampled or completely unexplored regions, such as Saudi Arabia, Syria, Iraq, eastern Turkey, and Iran, could lead to the discovery of additional Chaetopelma species or records, which would be beneficial in gaining more comprehensive insights into the taxonomy and distribution of this genus.

Almost all species of Chaetopelma are well illustrated, except for Ch. webborum, an enigmatic species known solely from the holotype female collected in Efulen (= Efoulen), Cameroon (Smith 1990). Despite Guadanucci and Gallon (2008) noting that this species does not belong to Chaetopelma, no further investigations have been conducted since then to clarify its taxonomic position, even though 15 years have passed since their publication. Although we were not able to study the holotype, based on the information provided in the original description, it is evident that this species is indeed misclassified. It differs from species of Chaetopelma in having stout and relatively short receptacles (vs long and thin), as well as pectinate tarsal claws (vs tarsal claws lacking teeth). Furthermore, its occurrence in Cameroon is significantly outside the known range of Chaetopelma (Fig. 5). The generic placement of this species should be revisited once the holotype specimen (NHM-03-6-30-22) becomes available for examination.

Finally, it is noteworthy that WSC (2023) has erroneously listed Ch. olivaceum (as well as one genus and 22 other species names) as authored by C.L. Koch in 1841, when in fact the correct date should be 1842, as noted in Simon (1892), Roewer (1942), and Bonnet (1956). In the taxonomic literature, Peters (1998) seems to be the first to incorrectly list the publication date for this species as 1841, a mistake that was later perpetuated by other researchers. This discrepancy likely stems from the WSC combining C.L. Koch’s 1842 publication with his volume from 1841, despite the clear distinction in their respective publication dates (Koch 1841, 1842).

We express our gratitude towards Amir Hossein Aghaei (Iran) and Mehdi Gavahyan (Iran) for generously providing us with their collected material and photographs. We also extend our thanks to Kari Kaunisto (Turku, Finland) for photographing the live specimen, Christian Langner (Münster, Germany) and Shaton Khezrpour (Sardasht, Iran) for kindly granting us permission to use their photos, Mahla Pourcheraghi (Iran) for providing us with a line drawing of the receptacles, and Yuri M. Marusik (Magadan, Russia) and two reviewers for commenting on an earlier draft of the manuscript.