Platypus of a scorpion:

1
Platypus of a scorpion genus Pseudochactas
Gromov, 1998 (Scorpiones Pseudochactidae)
Victor Fet1, Michael E. Soleglad2 Alexander V.
Gromov3 1Department of Biological Sciences,
Marshall University, Huntington, West Virginia,
USA 2Borrego Springs, California, USA
3Institute of Zoology, Almaty, Kazakhstan
2
ALEXANDER GROMOV, who in 1998 described Pseudocha
ctas the fourth lineage of extant
scorpions a lifetime discovery
3
Alexei Birula (1917) surveyed scorpions of the
Russian Empirea relict Calchas (Iuridae) at the
Turkish border some Euscorpius in Crimea and
Caucasus otherwise, a typical Palearctic arid
fauna (Buthidae), with a couple of endemic genera
in sand deserts of Central Asia.
Gary Polis (Biology of Scorpions, 1990, p. 251)
...only 14 species have been described for all
of the USSR (Fet, 1980) there are undoubtedly
more species undescribed...
A. Birula (1864-1937)
...NOBODY, however, expected Pseudochactas... and
the USSR was already gone anyway...enter
independent Uzbekistan
4
...UZBEKISTAN... THE SILK ROAD...THE HEART OF
CENTRAL ASIA...
?
?
...one of the only two doubly landlocked
countries in the world
5
Pseudochactidae Gromov, 1998 Pseudochactas
Gromov, 1998 Pseudochactas ovchinnikovi
Gromov, 1998
collected in 1994 by Sergei Ovchinnikov and Oleg
Lyakhov in Uzbekistan, and in 1995 by Sergei
Zonstein in Tajikistan
6

• Gromov (1998) noted that ... the new
  family... may be close to the common ancestor of
  all other scorpion families.
• Soleglad Fet (2001) demonstrated a separate
  and unique trichobothrial pattern of
  Pseudochactas, ...possibly ...the most primitive
  Recent scorpion.
• New material, collected in 2002, allowed to
  confirm and further study a separate, relict
  position of Pseudochactas (Soleglad Fet, 2003a,
  2003b).

7
A research grant from the National Geographic
Society supported the expedition of V. Fet and A.
Gromov in in April-May 2002 to Turkmenistan,
Uzbekistan, and Kazakhstan in search of scorpions
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a tiny (lt 30 mm), semitransparent, very
unimpressive scorpion...
9
??
10
in fact, way too unusual...to properly classify
Pseudochactas, we had to involve all major
character sets of all extant (and some fossil)
scorpion groups!

• The first platypus specimen, brought
  back by an early British expedition, was largely
  considered a hoax, constructed from parts of
  various animals. 

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A completely new trichobothrial pattern (the
major character set in scorpions Types A, B,
C (Vachon, 1974) from 34 to 100
trichobothria on pedipalp femur, patella
chela(Soleglad Fet, 2001)in Pseudochactas
(12 on femur, 10 on patella, 12 on chela). Looks
like a VERY PLESIOMORPHIC PATTERN
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Trichobothria high-level systematics
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Soleglad Fet (2001), in a cladistic analysis
based only on trichobothrial data (26
characters), placed Pseudochactas as a sister
group to the basal family Buthidae, as opposed to
all other extant scorpions
14
Pedipalp patella carination different from all
other scorpions, probably plesiomophic
15
Cheliceral dentition also a unique pattern
among modern scorpions (lacks a basal denticle
on movable finger an apomorphic loss!)
16
Metasomal carination (segment V) two ventral
carinae unique in extant scorpions but found in
the Carboniferous Palaeopisthacanthidae, a
sister group to all modern scorpion taxa
(Jeram, 1994)
17
Structure of venom gland simple, plesiomorphic
(no folds, which are a derived condition in many
other scorpion groups Soleglad Fet, 2003b)
18
Sternum morphology the MOST plesiomorphic
(Soleglad Fet, 2003a)
19
a DOUBLE ROW of spinules on leg tarsus unique
among extant scorpions
20
TARSAL SPINATION/SETATION IN SCORPIONS (Soleglad
Fet, 2003b)
a double row of socketed spines, Mesobuthus
(Buthidae)
a double row of non-socketed spinules
(Pseudochactas)
a double row of socketed setae, Isometrus
(Buthidae)
a single row of spinules, Nullibroteas (Chactidae)
21
High-level phylogeny of all extant scorpions
(Soleglad Fet 2003b) a cladistic analysis
based on 105 total and 33 fundamental
morphological characters was prompted and
inspired by the discovery of Pseudochactassubo
rder Neoscorpionesinfraorder Orthosterni4
parvorders 6 superfamilies14 familiessome
subfamilies tribes180 generaca. 2000 species
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a more detailed cladogram
Pseudochactida
Buthida
Chaerilida
Iurida
24
DNA sequence data also support a plesiomorphic
position of Pseudochactas (Soleglad Fet, 2003b)
mitochondrial 16S rRNA
nuclear 18S rRNA
25

• Pseudochactas therefore is assigned not only to
  a separate family, but also to its own
  superfamily, and parvorder (Soleglad Fet
  2003b). It represents the most basal lineage of
  extant scorpions.
• Fossil representatives of two other (more
  derived) parvorders are known from Cretaceous
  Iurida from South America (Carvalho Lourenço,
  2001) and Chaerilida from South Asia
  (Santiago-Blay et al., 2004) these fossils
  belong to three extant supefamilies
  (Scorpionoidea, Chactoidea, Chaeriloidea).
• The major lineages (parvorders) of extant
  scorpions could have been established in the time
  of Pangea (Permian/Triassic) early dinosaur
  time.

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Biogeography

• Pseudochactas undoubtedly is a relict, monotypic
  taxon (genus, family, superfamily, parvorder...)
• Restricted monotypic endemic relicts of high rank
  are rare
• Is there anything special about the locality of
  Pseudochactas in Central Asia?

27

• Pseudochactas could have been preserved in
  mild-climate, low mountains of Tajik Depression
  (700-1000 m a.s.l.).
• It could represent a remnants of the Mesozoic
  littoral fauna of the receded Tethys Ocean in the
  area later elevated by Tertiary tectonic uplift,
  while the surroundings underwent aridization.

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TWO KNOWN LOCALITIES Akmechet, Uzbekistan
3803' N, 6817' E Gandzhina,
Tajikistan 3758' N, 6834' E (Gromov, 1998)
UZBEKISTAN
TAJIKISTAN
AFGHANIISTAN
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Babatag Mts.
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GEOGRAPHY OF BABATAG

• Low (up to 2,000 m 6,000 ft) a.s.l. Babatag
  Range lies in the east of Surkhandarya Region of
  Uzbekistan. It is formed from Tertiary-Cretaceous
  rocks. In the west it borders the spurs of the
  Gissar Range.
• The region has the warmest winter and hottest and
  driest summer in Uzbekistan. With relatively low
  humidity, the air temperature in the daytime can
  reach almost 50º C 122 ºF. The period without
  frost in this region is one of the longest in
  Central Asia, from 226 to 266 days.

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Babatag Mts.
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Paleogeography

• Pseudochactas could represent an isolated faunal
  remnant of littoral fauna of the receded Tethys
  ocean. Important floral elements of littoral
  origin are found in low mountains of Uzbekistan
  and Tajikistan (Tajik Depression) (Kamelin,
  1979).
• Latitude of Tajik Depression shifted since the
  Paleozoic, e.g. in the Permian Pangea its
  paleolatitude was ca. 25º N (latitude of Miami)
  now it is 38º N (latitude of Washington, DC) --
  thus climate changed as well, from coastal marine
  to continental desert as India jointed Asia and
  the Tertiary mountains grew.

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South
?
Gobi,
"Amuria"
Ala Shan
?
?
Junggar
Tarim
Urals
Yili
?
Qilian Shan
East
Qaidam
European
?
Syr-Darya
Platform
?
Western
Ustyurt
Kunlun
Tajik
Block
Turan
W Hindukush
?
Karakum
Swell
Caucasus
P a l e o - T e t h y s
Eurasian part of Pangea in Late Permian, 260 Mya
(Heubeck, 2001)
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• Interestingly, Pseudochactas is the FIRST
  endemic of high rank (family, etc.) found in
  Central Asian mountains.
• There are species- and genus-level endemics of
  Tertiary origin in local flora and fauna but
  high-level endemics are rare in Central Asia
  (e.g. a desert rodent Selevinia, fam.
  Seleviniidae).
• We hear more about endemic families on island
  such as Madagascar, Hawaii or New Zealand.

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Babatag Mts.
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our field vehicle (a Soviet-made medical
emergency van)...
Pistachio tree (Pistacia vera L.)
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...friendly Uzbekistan/Tajikistan border guards
at their remote post
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... a lot of assorted ex-Soviet red tape.
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Pseudochactas an endemic relict
the oldest Monotremata only 123 Mya old
(Cretaceous) -- hairy upstarts!  
the oldest Rhynchocephalia only 225 Mya old
(Triassic)
the oldest Coelacanthiformes 400 Mya old
(Devonian), 2 species survive
the oldest Xiphosura Ordovician (ca. 500 Mya), 3
genera survive
The oldest scorpions are 430 Ma (Silurian)
Pseudochactas is the oldest surviving taxon
Gladiators (Mantophasmatodea), a recently
discovered, relict South African insect order,
should be quite old 2 species survive
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• What can we learn from such relict taxa as
  Pseudochactassole survivors of their lineage,
• veritable platypi, tuataras, or coelacanths
  of evolution?
• They may retain ancestral (plesiomorphic)
  features which are gone in other lineages
• They may contain unique (apomorphic) features
  which evolved only in this lineage
• They may reflect specific unique spots in the
  context of historical biogeography as relict
  taxa, which survived climatic and tectonic
  upheavals

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Further Ideas

• Biology unknown
• Definitely not a typical desert-adapted scorpion
  as are sympatric species of Buthidae
• Hibernates over summer (in cracks under roots)
• 2002 spring was late and cold on May 2-4,
  animals (males, females, young) were out next to
  a small temporary creek, or sai (arroyo, wadi),
  actively foraged on mud and wet stones
• Reproduction?
• Feeding?

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Babatag Mts.
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Other ObservationsSerrula on the ventral aspect
of cheliceral movable finger, probably a grooming
device, is heavily worn out in adults most
teeth broken
46
A sensory slit organ (on leg basitarsus)
47
Cuticle texture on leg tarsus, basitarsus, and
tibia could it be used for water diffusion?
48
cuticle texture changes upward from the basal
part of leg tibia
49
compare to a regular scorpion leg cuticle texture
(not only in desert forms)
Grosphus (Buthidae)
Euscorpius (Euscorpiidae)
Iurus (Iuridae)
50
Pectinal sensillae of Pseudochactas differ from
those of all other scorpion families (Fet
Brownell, in progress)
51
in conclusion,

• four major extant scorpion lineages are very
  ancient (think turtles, lizards, mammals, birds)
• many lineages contain relict taxa
• many corners of the world have not yet been
  seriously blacklighted
• new finds could yield new and possibly very
  important pieces of the relict scorpion puzzle

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Acknowledgements
to Alex Elena Kreuzberg (IUCN Snow Leopard
Programme) for their hospitality in Tashkent, and
help with field logistics during Uzbekistan
travels
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Acknowledgements

• and to National Geographic Society for funding
  the Uzbekistan trip of V. Fet and A. Gromov in
  April-May 2002

• to David Neff for his brilliant SEM work