Scyllacerta

Scyllacerta Temporal range: Late Permian, early–middle Wuchiapingian, ~257 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
SAM-PK-K7710, the holotype aggregation of Scyllacerta
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Neodiapsida
Family:	†Younginidae
Genus:	†Scyllacerta Jenkins et al., 2026
Species:	†S. creanae
Binomial name
†Scyllacerta creanae Jenkins et al., 2026

Scyllacerta is an extinct genus of neodiapsid stem-reptile known from the late Permian (Wuchiapingian age) Teekloof Formation (Endothiodon Assemblage Zone) of South Africa. The genus contains a single species, Scyllacerta creanae, known from a preserved aggregation of at least six articulated individuals, four of which have articulated skulls. This specimen was originally identified as immature individuals of the closely related genus Youngina, but it is now classified as a distinct member of the stem-reptile family Younginidae, of which it is the oldest known member. It is also the oldest unambiguous neodiapsid. Scyllacerta bears a tympanic fossa on the back of its skull, suggesting that the middle ear of living reptiles was present in their Permian ancestors. Despite the small size of the known Scyllacerta individuals compared to Youngina, they likely represent nearly mature animals.^[1]

History

Discovery

Geological context of the Teekloof Formation

In the early 1900s, Roger M. H. Smith conducted extensive fieldwork in the Hoedemaker Member of the Teekloof Formation of South Africa, with the purpose of cataloging and describing the taphonomy of vertebrate fossils in the region's floodplain deposits. Smith, with the assistance of Annelise Crean and Paul October, collected 329 separate fossil specimens in three outcrop localities: Wilgerboschkloof, Leeukloof, and Dunedin (named after the farms on which the excavations took place). These outcrops are part of the Endothiodon Assemblage Zone (EAZ).^{[nb 1]} Smith published the results of this work in 1993, concluding that the outcrops of the Hoedemaker Member could be classified using their sedimentological characteristics and the taphonomic aspects of preserved vertebrate fossils; "channel bank" and "distal floodplain" outcrops are generally comparable in the rarer preservation of vertebrate fossils and prevalence of isolated skulls and postcranial bones, while "proximal floodplain" deposits preserve, vertebrate fossils more commonly, with a wide range of taphonomic preservation modes and proportionately more specimens found in anatomical articulation (bones in lifelike positions).^[5]

Research history

One fossil in particular, an aggregation of several small, articulated reptiles embedded in micrite-cemented siltstone, was collected by Smith from Leeukloof 43. It was prepared by Annelise Crean using a dental drill and needle, and then permanently accessioned at the Iziko South African Museum (SAM) as specimen SAM-PK-K7710. In 1995, Smith and Susan E. Evans published an initial description of this specimen, identifying five individuals of similar size, preserved in lifelike positions. They recognized that these specimens are about half the size of those referred to Youngina, another early reptile from younger (more recent) rocks in South Africa. While they acknowledged the possibility that these newly-discovered individuals could belong to a new taxon, they concluded that they likely belong to immature Youngina individuals. They further noted that these individuals were found in stratigraphically lower rock outcrops, making them around three million years older than Youngina.^[6] The following year, Smith and Evans published a more detailed description and analysis of SAM-PK-K7710. In addition to the five nearly-complete, articulated skeletons (labeled a–e), they identified a sixth individual (f), represented by an isolated hindlimb. Based on the observable anatomy, they remarked these individuals show "no marked morphological differences" from Youngina, based on previous descriptions of this taxon. Based on the closure of the neurocentral sutures, ossification of the tarsals and carpals, close proximity of elements of the pectoral and pelvic girdles, and fusion of the sacral and caudal ribs to their respective vertebrae (all indicators of at least partial maturity), the researchers concluded the individuals are not hatchlings, despite their small size. However, various features are also apparent indicators of skeletal immaturity, including the lack of sculpturing and complex sutures on the skull roof bones, proportionately large eyes and parietal foramen, and weakly ossified sternal plates.^[7]

Due to the perceived importance of Youngina as an "archetypal" diapsid reptile representing the ancestral anatomical condition for the reptile skull, the description of SAM-PK-K7710 was seen as a valuable contribution, as it preserves most of the postcranial skeleton, whereas Youngina had previously been known from almost entirely cranial remains.^[7] As such, many later researchers incorporated it as a specimen of Youngina in phylogenetic analyses including this taxon, in the context of the evolutionary relationships of early reptiles.^[8] In a 2021 description of the anatomy and relationships of the Permian Weigeltisaurus of Germany, Adam C. Pritchard and colleagues included SAM-PK-K7710 in their phylogenetic analysis, but as an entity distinct from Youngina, given significant differences they observed between skull and limb anatomy of the two.^[9]

In February 2025, Mooney, Scott, and Reisz described Akkedops bremneri as a new early reptile from South Africa. These authors established SAM-PK-K6205, an isolated skull and fragmentary postcrania, as the holotype (name-bearing) specimen, and referred BP/1/2614 (an isolated and crushed skull) and SAM-PK-K7710 to this species, incorrectly claiming they had all been collected at the same site. They further suggested that the cranial anatomy of all three specimens is indistinguishable, supporting their referral to a single taxon, distinct from Youngina.^[10] In their 2025 redescription of Galesphyrus, a more distantly related Permian South African sauropsid, Buffa and colleauges questioned the referral of SAM-PK-K7710 to Akkedops, and restricted their phylogenetic scoring of this taxon to just its holotype, SAM-PK-K6205.^[11]

Naming

In 2026, Xavier A. Jenkins and colleagues published a redescription of SAM-PK-K7710 based on high-resolution synchrotron μCT scans of the specimen. They identified numerous anatomical characters distinguishing it from both Akkedops and Youngina. Furthermore, a review of discovery localities for the involved specimens showed that the Akkedops holotype (SAM-PK-K6205) was collected more than 180 kilometres (110 mi) away from Leeukloof 43, in a higher (more recent) assemblage zone, the Cistecephalus AZ, at Matjiesfontein 167. BP/1/2614 was also collected at a distinct locality in the even younger Daptocephalus AZ. As such, they described SAM-PK-K7710 as belonging to a new genus and species of younginid, Scyllacerta creanae. SAM-PK-K7710a, the most complete individual of those preserved in the aggregation, was selected as the holotype of the species.^[1]

The generic name, Scyllacerta, combined a reference to Scylla, a hybrid monster in Greek mythology described as inhabiting a cavern, bearing many heads, and having multiple rows of teeth, with lacerta, a Latin word meaning 'lizard'. This name was chosen as SAM-PK-K7710 represents an aggregation of multiple individuals (with multiple skulls) preserved in a 'cavern' (burrow), with each skull bearing many rows of palatal teeth. The specific name, creanae, honors Annelise Crean, the preparator of the specimen.^[1]

References

1. Jenkins, Xavier A.; Buffa, Valentin; Marchant, Cy J.; Ford, David P.; Browning, Claire; Fernandez, Vincent; Dollman, Kathleen; Botha, Jennifer; Choiniere, Jonah N.; Benson, Roger B. J.; Peecook, Brandon R. (2026-01-22). "The origin of the tympanic fossa in reptiles revealed by a late Permian neodiapsid". Palaeontology. 69 (1) e70041: 1–15. doi:10.1111/pala.70041. ISSN 0031-0239.
2. Keyser, André W.; Smith, Roger M. H. (1978). "Vertebrate biozonation of the Beaufort Group with special reference to the Western Karoo Basin". Annals Geological Survey South Africa. 12: 1–36.
3. Rubidge, Bruce S., ed. (1995). Biostratigraphy of the Beaufort Group (Karoo Supergroup). Biostratigraphic Series 1. Pretoria: Department of Mineral and Energy Affairs, Geological Survey. pp. 1–46. ISBN 978-1-875061-24-2.
4. Day, Michael O.; Smith, Roger M. H. (2020-06-01). "Biostratigraphy of the Endothiodon Assemblage Zone (Beaufort Group, Karoo Supergroup), South Africa". South African Journal of Geology. 123 (2): 165–180. doi:10.25131/sajg.123.0011. ISSN 1996-8590.
5. Smith, Roger M. H. (1993-02-01). "Vertebrate taphonomy of Late Permian floodplain deposits in the Southwestern Karoo Basin of South Africa". PALAIOS. 8 (1): 45–67. doi:10.2307/3515221. ISSN 0883-1351.
6. Smith, Roger M. H.; Evans, Susan E. (1995). "An aggregation of juvenile Youngina from the Beaufort Group, Karoo Basin, South Africa". Palaeontologia Africana. 32: 45–49.
7. Smith, Roger M. H.; Evans, Susan E. (1996). "New material of Youngina: evidence of juvenile aggregation in Permian diapsid reptiles" (PDF). Palaeontology. 39 (2): 289–303. Archived (PDF) from the original on 2019-07-30.
8. Ezcurra, Martín D. (2016-04-28). "The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms". PeerJ. 4 e1778. doi:10.7717/peerj.1778. ISSN 2167-8359. PMC 4860341. PMID 27162705.
9. Pritchard, Adam C.; Sues, Hans-Dieter; Scott, Diane; Reisz, Robert R. (2021-05-20). "Osteology, relationships and functional morphology of Weigeltisaurus jaekeli (Diapsida, Weigeltisauridae) based on a complete skeleton from the Upper Permian Kupferschiefer of Germany". PeerJ. 9 e11413. doi:10.7717/peerj.11413. ISSN 2167-8359. PMC 8141288. PMID 34055483.
10. Mooney, Ethan Dean; Scott, Diane; Reisz, Robert Raphael (2025-02-26). "A new stem saurian reptile from the late Permian of South Africa and insights into saurian evolution". Swiss Journal of Palaeontology. 144 (1): 10. doi:10.1186/s13358-025-00351-y. ISSN 1664-2376. PMC 11865139. PMID 40027993.
11. Buffa, Valentin; Jenkins, Xavier A.; Benoit, Julien (2025-11-17). "Galesphyrus capensis from the Permian of South Africa and the origin of Neodiapsida". Journal of Systematic Palaeontology. 23 (1) 2563582. doi:10.1080/14772019.2025.2563582. ISSN 1477-2019.

Notes

1. The nomenclatural history of Karoo Supergroup assemblage zones (AZ) is convoluted, and their classifications have been extensively modified. At the time of Smith's publication, the EAZ was referred to under a two-name system, as the Tropidostoma–Endothiodon AZ.^[2] This was later simplified to the Tropidostoma AZ,^[3] before being combined with the Pristerognathus AZ in 2020 to form the Endothiodon AZ.^[4] Within the EAZ, Scyllacerta is more precisely placed in the Tropidostoma–Gorgonops subzone.^[1]