Pachypanchax
Pachypanchax Myers, 1933 may thus be diagnosed as follows: Maxillary relatively
immobile, bound at its posterior end to the preorbital by a fold of skin. Premaxillary
ascending processes flat and broad, tapered posteriorly and not overlapping in the midline.
A single pair of tubular nares present. Reflective pineal spot absent. Frontal squamation
typically of the E-type, with prominent H scales. In very large specimens, a shallow pit
may be present in the center of some scales along the midlateral line, but there is no
evidence of any connection to an underlying neuromast. Scales and fin rays lacking
papillae. Haemal arches unexpanded, no pleural ribs on haermal spines. Hypural plates
fused to form a hypural fan in adults, joint lines visible in juveniles. Caudal fin rounded or
rounded-truncate, the middle rays never extended. Basal third to three quarters of caudal
fin heavily scaled, the scales in straight rows, one scale wide, each series covering the
interspace between two caudal rays. Caudal fin lacking a median lobe. Filamentous
extensions of the dorsal and anal fins of males variably present. Dark gular bar variably
present. Pigmentation pattern does not include cross bars on body. Basal dorsal-fin spot
absent in males, variably present in females. Type species: Pachypanchax playfairii
(Gunther 1866).
The genus is endemic to Madagascar and the granitic Seychelles. The Zanzibari
population of Pachypanchax playfairii represents a recent translocation and (Parenti
[1981] notwithstanding) there are no confirmed records of this species from the East
African mainland (Seegers, 1980). Apart from two species native to eastward- and
northward flowing drainages in the extreme north, Malagasy Pachypanchax are restricted
to the island’s western versant, from the Ambohitra Massif (Massif d’Ambre) south to the
basin of the Tsiribihina River
No photos exist.
From Paul Loiselle's review of Pachypanchx: Guichenot (1866) described Poecilia nuchimaculata from a single specimen collected
by J. P. Goudot, a French resident of Madagascar from 1835 until his death in the early
1860's. The specimen lacks precise locality data and as Goudot’s journals were lost when
he disappeared while in the field (Dorr, 1997), subsequent efforts to determine its
provenance have proved fruitless. Published data (Huber, 1998) indicate that with regard
to both morphometric and meristic characters the type falls within the range that defines
the Malagasy representatives of the genus Pachypanchax. He noted that the prefrontal
scales of this specimen are smaller than those of other Pachypanchax species, while the
lateralis system consists of open rather than enclosed pores. The caudal squamation is
rather light, with scales present only on the basal third of the fin (de Soutter, pers. com.), a
feature shared with only one other Malagasy congener. Radiographic examination of the
caudal skeleton confirms Huber’s observation that a shallow notch separates the upper
plate, formed by the fusion of third, fourth and fifth hypural bones and the lower plate,
formed by the fusion of the first and second bones. This condition is more reminiscent of ZOOTAXA
that found in many representatives of the Nothobranchidae (upper and lower plates
separated by a deep groove), than that seen in Aplocheilus (hypural skeleton made up of
three independent elements, the upper- and lowermost comprising the fused fourth and
fifth and first and second hypural bones respectively).
In the absence of additional material of P. nuchimaculatus, there is no way to
determine whether the observed anomalies in squamation and caudal skeleton of the type
specimen are idiosyncratic or reflect significant population-level differences. Pending the
acquisition of additional material of this species, it seems advisable to follow Parenti
(1981) and provisionally assign Poecilia nuchimaculata to the genus Pachypanchax
OMO has been around a very long time but Loiselle when he went back to collect from the original collection point he found a different fish actually a new species he named ARN. OMO and ARN don't live anywhere near each other.
"The most primative of all killies they are in every sense of the word living fossils". - Paul Loiselle
Distribution in Madagascar
P. playfairi is from the Seychelles Islands which are just north of Madagascar the other species are all endemic to Madagascar.
Madagascar is a fragment of the southern tip of the ancient super-continent Gondwanaland that split off from continental Africa about 120 million years ago, India split off from this fragment 65 million years ago.
Completely isolated from all other life evolution slowed down as there were far fewer things to adapt to. The Pachypanchax that were in India where were the same as the ones in Madagascar before the split began changing in their new surroundings and became Aplocheilus while Pachypanchax still in Madagascar didn't really change.
The geography of Madagascar is fairly simple, it's a thousand miles long and there's mountains in the middle. The east coast is a permanent rain forest because of the moisture laden air blowing from the Indian Ocean. Bedotia are found here. The west cost is dry and sandy. Pachypanchax live here except for the one location where one species lives on the other coast.
Madagascar is home to the Tenerec, the insectivore that is the smallest mammal known and the most primitive of primates: the lemurs.
Or as Loiselle refers to them: "tree poodles".
I have a problem with the Lemurs, not that I do not like the Lemur, in fact I've never met a Lemur I didn't like, they're very amiable animals. But, mention you work in conservation in Madagascar and the first thing anybody says is "we have to save the Lemur". Well let me tell you something. Every Lemur known to science in 1900 is with us today and that is not true of the fish of Madagascar."
- Paul Loiselle
Two species of Pachypanchax seem to have gone extinct in the same time frame as have other Malagasy fish.
Aplocheilus
Pachypanchax
Upper Jaw:
mobile
immobile
Haemal Arches:
expanded
unexpanded
Hypural Bones:
not fused
fused
Caudal:
ovoid
rounded
Caudal Median Rays:
prolonged
not prolonged
Caudal Base:
unscaled
1/3 - 3/4 scaled
Pineal Spot:
present
absent
Aplocheilus Photos roughly 5:2
Pachypanchax Photos roughly 5:3
Aplocheilus are just narrow Pachypanchax
"Myers (1933) based the genus Pachypanchax upon four diagnostic characters: (1) limited
mobility of the maxilla, resulting from its attachment posteriorly by the skin to the
postorbital region of the skull; (2) presence of unexpanded haemal arches; and (3) a
rounded caudal fin whose (4) basal half is heavily scaled, the scales in straight rows, one
scale wide, each series covering the interspace between two caudal rays. Myers placed
particular emphasis on the caudal squamation of Pachypanchax, which he found to be
unique among Old World aplocheilid cyprinodonts examined by him, and matched only by
that of the Neotropical genus Austrofundulus."
Loiselle 2006
Thus Austrofundulus is another missing link, it has not yet evolved any further with regard to caudal scalation any more
than the Pachypanchax it evolved from.
This shows the breakup of the Gondwanaland super-continent and the origin of Madagascar, India and the Seychelles where P. playfairi is the sole freshwater fish.
150 million years ago a piece the the Antarctic continenal mass split off.
120 million years ago it had totally separated from Antarctica.
105 mya and Africa and the Indian subcontinent moved north.
90 MYA was a big time for killies. By now the Indian subcontinent was at the equator. We believe the greatest amont of divestidicauton began about 80-90 mya. This is when modern killifish began to emerge. India and Magagascar split.
the Indian Ocean. Bedotia are found here. The west cost is dry and sandy. Pachypanchax live here except for the one location where one species lives on the other coast.
