The Emperor is back! Rediscovery and redescription of the holotype of Pandinus imperator (Scorpiones: Scorpionidae)

The holotype of the Emperor Scorpion Pandinus imperator (C.L. Koch, 1841) was long believed to have been lost. In 2015, as scientists at the State Museum of Natural History in Stuttgart were digitizing its entomological collections, they rediscovered the specimen on which Koch had based his description of the scorpion in 1841.

The Emperor Scorpion is one of the world's most famous scorpions mainly due to its large size.Its impressive size, together with the large chelate pedipalps, harmless sting and its easy breeding in captivity, led this species to become a popular pet for arachnid keepers.Therefore, the ever increasing demand of this species for breeding has led to it being added to the list of animals protected by the Washington Convention (Lourenço & Cloudsley-Thompson 1996, Rossi 2015b, 2015d).
In the wild, the species is distributed in the moist and wet tropical forests of West and Central Africa, approximately from Liberia to Cameroon (Prendini 2004, Rossi 2015b).However, its precise distribution has by no means yet been conclusively determined.
The type specimen of Pandinus imperator was considered lost (Moritz & Fischer 1980, Lourenço 2014).During the digitalization of the collections at the State Museum of Natural History in Stuttgart, a drawer labelled "Holotypus: Buthus imperator KOCH 1842" containing several scorpions turned up.One of these scorpion specimens bore great resemblance to Koch's description (Koch 1841) and coloured drawing (Figs 1-2).

Results
Having considered all the available evidence, we conclude that the specimen in question is the holotype of Pandinus imperator.It agrees well with both the original description and the original illustration (colour, total length, 16 pectinal teeth, etc., see Figs. 2-4) (Koch 1841).The colour of the specimen agrees with the hand-coloured figure on Koch's plate and ranges from brown to ochre.In our opinion, this could be due to bleaching.Koch described the specimen from the Erlangen University collection, where it had possibly been presented in an earlier exhibition.Unfortunately, no locality is indicated on the label nor in the original description.
Recent measurements: prosoma: 22.8 mm, mesosoma: 56.4 mm, metasoma and telson: 81.7 mm (i.e., including vesicle and aculeus, with the length of the first segment interpolated); total length: 160.9 mm (measured by a vernier calliper, in view of the fact that the telson is coiled up; see Fig. 3).Most of the first metasomal segment of the specimen is missing.The metasoma has been torn from the mesosoma and is now connected by a straw.This was probably as a result of later handling since there is no reference to any damage in Koch's (1841) description.A comparison with the plate figure makes it clear that the tip of the stinger also suffered subsequent damage (Fig. 3).
As Koch's method of measurement for the carapace, mesosoma, metasoma and telson is not clear, the measurements do not agree completely with the specimen.It is also feasible that Koch used a different measuring unit than that assumed (e.g., 'Bavarian lines', 'Rheinland Zoll').The total length nevertheless appears to be consistent with the value measured in the rediscovered specimen.If we take into account the missing part of the first metasomal segment and the broken aculeus, the possible total length of the specimen is approximately 170 mm, similar to that reported by Koch using the Bavarian decimal Zoll.On the other hand, if Koch used the French Zoll, the total length adheres to the values which can now be measured in the damaged specimen.This being the case, the original drawing was possibly manipulated to represent a complete specimen despite the missing parts.Redescription of the holotype Type material: ) holotype (dry, SMNS-Scor-002031), unknown locality.Description: Measurements in Fig. 2. Total length 160.9 mm.[Possible total length including the missing broken parts about 170 mm.] Base colour brown to reddish brown; pedipalp brown to reddish brown with chela palm yellowish to orange-brown and fingers brown; carapace brown; tergites brown; sternites yellowish brown; pectines and genital operculum pale yellow; legs from brown (femur) to yellowish (tarsomere); chelicerae yellowish with fingers brown; metasoma brown and telson yellowish to brown.Carapace with many fine granules mainly on anterior and lateral sides.Carapace with a V furrow on its anterior border and a low triangular median depression on the posterior side.Median eyes grey and closer to posterior border of carapace.Lateral eyes three in number and grey.Tergites generally smooth with some fine granules on VII tergite.Sternites smooth.Stigmata very long and narrow.Genital operculum is damaged.Pectines with 16/16 teeth form an angle of approximately 120°.Sternum pentagonal almost identical in length and width.Coxoapophysis of reddish yellow and longer than wide.Chelicerae with two denticles on the fixed finger and four denticles on the movable finger (Vachon 1963).Pedipalps with very few and short setae, on chela fingers only.Trochanter and femur tuberculated on anterior and superior side.Patella generally smooth.Chela very wide and round, dorsally with rounded granules, rarely conical or pointed; ventral surface with several granules.Chela with 3 internal trichobothria (Fig. 5) and 9 ventral trichobothria (Fig. 6).Patella with 32 ventral trichobothria (Fig. 7).These numbers correlate on left and right pedipalp.Fixed and movable fingers all have six/seven subrows of granules which forms a single line.Type C trichobothrial pattern (Vachon 1974).Tarsomere II with 2 spines on the inclined antero-ventral surface.Spine formula of tarsomere II: 4/3: 4/3: 4-5/3: 4-5/3.Metasomal segments with 8-8-8-8-7 carinae; latero-ventral carinae almost completely absent on segments I, II, and III.Ventral carinae smooth on segments I, II, and III, with some granules on segment IV and moderately pointed on segment V. Dorsal carinae on metasomal segments pointed.All segments longer than wide but metasomal segment I badly damaged and cannot be studied.Telson with only a few short setae.Vesicle piriform; its ventral surface showing several granules.Aculeus long, but broken at the tip.

Discussion
The specimen undoubtedly belongs to what is presently known as the species P. imperator.In fact, it clearly differs from the two most closely related species, Pandinus ulderigoi Rossi, 2014 from the Central African Republic and Pandinus gambiensis Pocock, 1900 from Senegal, Mali, Guinea-Bissau and Gambia (Vachon 1967, Rossi 2014, 2015a, 2015b, 2015c, 2015d).There has been some confusion as to the correct year of description for Buthus imperator; a matter already discussed by Brignoli (1985).Although Koch's 9 th Volume of "Die Arachniden" was published in 1842, the first 56 pages, containing the description of Buthus imperator, had already been published in 1841.Due to article 21.5 of ICZN (2017) the year 1841 is therefore correct.
It remains a mystery as to how these specimens found their way into the collection at the National History Museum in Stuttgart in the first place.The SMNS is starting a project to digitize its archives of printed and handwritten historical documents.We hope, these efforts will also result in hints to clarify the accession of these scorpion specimens.