Table Of ContentBijdragentot deDierkunde, 63(3) 129-148(¡993)
SPBAcademie Publishingbv, TheHague
The taxonomic significance of the short-shafted mesotriaene reviewed by
parsimony analysis: validation of Pachastrella ovisternata Von Lendenfeld
(Demospongiae: Astrophorida)
Manuel Maldonado
Centre d'EstudisAvançais deBlanes, CamideSantaBarbara s/n, 17300-Blanes,Girona, Spain
Keywords: Astrophorida, Pachastrellidae, parsimony analysis, sponges, taxonomy
Abstract nuevoejemplarpruebaqueP.ovisternataesunaespecieválida
ycorrobora laexistenciademesotrienas derabdoma corto enes-
pecies del géneroPachastrella.
The spiculecomplementofademospongespecimen collected
from theAtlantic coastofSpainwasnotedtobesimilar tothat Los análisis deparsimoniamuestran quela especie Yodomia
ofPachastrella monilifera,butparticularlycharacterizedbythe perfecta, tradicionalmente asignada al género Yodomiapor la
presenceofshort-shaftedmesotriaenes. Afterdetailed examina- presencia de mesotrienas,deberíaserreclasificada enel género
Pachastrella, cercadeP. ovisternata. Los análisisindican tam-
tion,it wasconcluded thatthe specimenundoubtedlybelonged
tothe species Pachastrella ovisternata Von Lendenfeld, 1894. bién que las mesotrienas que aparecen en Calthropellidaey
For a longtime,this species has been regardedasynonym of Pachastrellidae sonelresultado deunaevolución convergente en
laforma delasespículas tetraxonas deestos dosgrupos.Elestu-
Pachastrella moniliferaSchmidt, 1868.Examination ofthisnew
specimenshowed thatPachastrella ovisternata wasavalid spe- dio anivelespecífico indicaquelasmesotrienas han surgidomás
de unavez enel senodela familiaPachastrellidae. Portanto,
ciesofthegenusPachastrella.Moreover,itdenotedthereal exis-
tenceofmesotriaenes in this genus. lapresencia demesotrienas nopuedeser considerada,ensímis-
Theparsimony analyses indicated thatthe species Yodomia ma, comouncarácterdiagnósticoanivel degénero.Sinembar-
perfecta, traditionallyassigned to the genus Yodomia by the go,sehamostrado comouncaráctermuy fiable paradistinguir
presence ofmesotriaenes,oughttobereclassified in the genus taxones anivel específico.
Pachastrella,closetoP. ovisternata. Theseanalysesalsoshowed
that mesotriaenes are a product of aconvergent evolution in
Introduction
shapeof tetraxon spiculesin Calthropellidaeand Pachastrelli-
dae. At the species level it is suggested that short-shafted
mesotriaenes have arisen morethan oncein the family Pacha- Demosponges with short-shafted mesotriaenes
strellidae. Thus, thepresence of mesotriaenes itselfcannot be (mesocalthrops or mesodichotriaenes) are extreme-
regardedasadiagnosticcharacteristicatgenericlevel. However, ly rare. According to the literature, these spicules
it wasnoted tobe areliable featurein order to distinguishtaxa
are present in species belonging to the family
atspecific level.
Calthropellidae, such as Pachastrissa pathologica
(Schmidt, 1868) (sensu Von Lendenfeld, 1903;
Resumen Levi, 1973)andPachataxaenigmatica Lévi& Lévi,
1983. They alsooccur insomepachastrellids, such
Laespiculacióndeunejemplardedemosponjaprocedentedelas as the species of the genera Yodomia Lebwohl,
costasatlánticasespañolasseapreciómuy similaraladePacha- 1914(sensu Dendy, 1916) and Triptolemus Solías,
strella monilifera, pero caracterizada por la presencia de 1888.Additionally, apeculiar caseofshort-shafted
mesotrienas derabdoma corto.Tras unestudio detallado seha mesotriaenes becoming desmas has been reported
concluido quedichoejemplarpertenecealaespeciePachastrella
ovisternataVonLendenfeld,1894.Estaespecie,sinembargo,ha by Lévi & Lévi (1989) in the enigmatic genus
sido considerada,desde hace mucho tiempo,unsinónimo de BrachiasterWilson, 1925.
Pachastrella moniliferaSchmidt, 1868. La descripción deeste Many of these descriptions of species with
130 M. Maldonado- Taxonomicsignificance of themesotriaenein Astrophorida
mesotriaenes are very ancient. Furthermore, most (MNCN: 36, accordingto the old code), Sphinctrellagracilis
species have not been recorded since their initial Solías, 1888 (BMNH: 94:11:16:144 to146),Sphinctrellahorrida
description, except inafew cases. Insuch cases,the Schmidt,1870 (BMNH: 70:5:3:47),SphinctrellacribriferaSol-
las, 1888 (BMNH:89:1:1:39),and CalthropellasimplexSolías,
shortlistsof records indicatethatthese species are
1888 (BMNH: ?, schizotype stored as substratum of S. cri-
usually limitedto asmallgeographical area.Conse- brifera). Inaddition,somespecimenscollected in the Alboran
quently, mostofthesespecies are presently regard- Seabelongingtothe species cited below, werealso examined:
ed as taxonomieoddities.The genus Yodomia,for Pachastrella moniliferaSchmidt, 1868,Poecillastra compressa
instance, has virtually been forgotten by present- (Bowerbank, 1866),Poecillastra amygdaloides (Carter, 1876),
Spinctrella verrucolosa Pulitzer-Finali, 1983,Stoeba plicatus
day taxonomists, althoughitwas never invalidated.
(Schmidt, 1868), Dercitus bucklandi (Bowerbank, 1861) and
Consequently, the existence of diverse types of Pachastrissa pathologica(Schmidt, 1868). Other datarequired
mesotriaenes has unfortunately goneunnoticedin were obtained from descriptions in scientific literature.
interesting discussions on the evolution and rela- The skeletal study was accomplished using the standard
tionships ofthe tetraxon spicules (e.g., Reid, 1970; methodology(Riitzler, 1978).Micrographswereobtained using
aHITACHI-S-2300SEM.
Levi, 1991). The taxonomie history of the genus
Theparsimonyanalyses wereperformedusing "Paup3.0g"
Brachiaster, which was recently reclassified from (Swofford,1989),accordingtotheassumptionsexplainedinthe
Lithistida "incertae sedis" (Wilson, 1925) to As- text.
trophorida, Pachastrellidae(Lévi &Lévi, 1989)and
subsequently relocated in LithistidaTetracladina
(Lévi, 1991),isalso indicativeofthesystematic in- Systematic description
stability affecting most ofthespecies concernedin
this study. Genus Pachastrella Schmidt, 1868
The collectionof a new pachastrellid specimen
with mesotriaenesprompted the present investiga- PachastrellaovisternataVon Lendenfeld, 1894
tion on the relationships between taxa that have (Fig. 1; Pis. I-III)
short-shafted mesotriaenes, using parsimony anal-
ysis. Synonymy. - Pachastrella ovisternata Von Lendenfeld, 1894:
439.
Pachastrella monilifera(Schmidt);Topsent, 1902: 14; 1904:93,
Materialsand methods 94(inpart).
Non: Pachastrella ovisternatasensuFerrer-Hernández, 1914:7
The specimendescribed herewascollected duringanexpedition (=P. monilifera).
carried outin 1982by the Spanish Institute ofOceanography.
Thelocation datawere:muddybottomat300mdeep,nearCape Description. - Massive specimen, irregular in
Finisterre (northeasternAtlanticcoastofSpain);latitude/longi- shapeand 20 x 20 x 14cm insize(Pl. I). Thesur-
tude areunknown. Thespecimenwaspreserveddryanddeposit- faceis uneven, wrinkledinsome areas and usually
ed in the Museo Nacional de Ciencias Nacionales in Madrid
covered with slime. Ostia are circumscribed to a
(MNCN-01.01/6). The holotype of Pachastrella ovisternata,
borrowed fromthe Naturhistorisches Museum Wien (NMW- large concave area resulting from a convoluted
Inv.Nr. 525and 526)wascheckedagainstthe collected specimen fold. Non-aquiferous conical papillae, 5-8 mm in
and material described by Ferrer-Hernández (1914) under the height, along with hispidating tracts, protruding
nameofPachastrella ovisternata(MNCN-202&203,according 3-4mm, present on the inhalantsurface. Oscules
tothe old code).
are 1-2mmindiameter,scatteredontheremaining
Typematerial and abundant othermaterial stored in theBrit-
ish MuseumofNaturalHistoryin London (BMNH),theMuseo surface. Colour greyish white. Stony consistency
Civico di Storia Naturale "G. Doria" in Genoa (MSNG) and when dry.
MNCN were examined in order to adequatelyrecord charac-
teristics atgenericlevel. Typematerial examinedwasasfollows: Spicules:
Characellapachastrelloides(Carter, 1876) (BMNH: 10:1:1680
Oxeas: curved or slightly flexuous, blunt-pointed
and 1681), Characella tripodaria (Schmidt, 1868) (BMNH:
68:3:2:36),Poecillastra rudiastra Pulitzer-Finali,1983 (MSNG: (Figs, la, b), 3600-7500 m X 16-45 insize.
C:E:47161), Sphinctrella linaresi Ferrer-Hernández, 1914 Calthrops and pseudocalthrops: clads are usually
Bijdragen tot deDierkunde, 63 (3) - 1993 131
Fig. 1.SpiculesofPachastrella ovisternata:(a)oxeas,(b)bluntendofoxea,(c)calthrops,(d)dichotriaene,(e)mesotriaene,(f)metaster,
(g)amphiasters,(h) plesiasters,(i) oval microstrongyles, (j)microrhabdoid streptaster.
132/I M. Maldonado- Taxonomicsignificance of the mesotriaenein Astrophorida
Plate I.Overall view ofthe specimen.
straight in the smaller forms, but malformations Oval microstrongyles: usually elliptical in shape,
are occasionally observed inthegreater forms(Fig. fully covered with minutespines (Fig. li, PI. Hid)
lc, PL lib). Clads display a wide range in size, and 12-19/¿m x 5-9 in size.
measuring 122-1100¡¿m x 8-55/¿m. Microrhabdose streptasters: thin, very long forms
Dichotriaenes:short-shafted, occasionally withone (25-45/¿m x 1-2fim),exhibiting strongspines or
or two undividedclads only (Figs. Id, e, Pl. lia). microspiny turbercles (PI. IIIc; Fig. lj). They are
The rhabdomemeasures 65-85 ¿im X 8-12 /¿m, scarce. Thethick centralaxisalong withthegroups
theprotoclads 25-40/nm x 8-12/im,andthedeu- of minute degenerate actines (resembling spines)
teroclads46-95 x 7-10/im.The rhabdomeis made these spicules resemble polytylote micro-
usually shorter than theclads. strongyles when examined under the light micro-
Mesodichotriaenes: similar toshort-shafted dicho- scope.
triaenesinwhich theshaft(rhabdome sensulato) is Similarspicules have beenreported in some spe-
prolonged onbothsidesofthe cladomeforming a cies of TriptolemusSolías, 1888, Pachastrella, and
rhabdome sensu stricto and an epirhabdome. Yodomia. They were initially described as mi-
Epirhabdome usually shorterthanrhabdomesensu croxeas or derivedspicules (e.g.,Carter, 1876; Sol-
stricto (Fig. le; Pl. Ile, d). Clads are always di- las, 1888;Kirkpatrick, 1903), sometimesunder the
chotomous and no malformationswere observed. ambiguous name of "microrhabds" (e.g., Kirk-
Dimensions are similar to those of the dicho- patrick, 1902; Pulitzer-Finali, 1971). However, I
triaenes. Epirhabdome measures 40-85 /im x agree with authors such as Dendy (1916: 234),
7-12 )j.m. Sarà(1959) and Lévi&Lévi(1983: 153), who have
Bijdragen tot deDierkunde, 63 (3) - 1993 133/II
Plate II.Megascleres: (a) dichotriaene,(b) calthropsand dichomesotriaene,(c) & (d) different views ofdichomesotriaenes.
interpreted these spicules as reducedstreptasters. consistency to the sponge.A thick crust(1-1.5 ¿¿m)
Amphiasters: with short shaftand microspiny ac- of microstrongyles reinforces the ectosome. The
tines. Microspines are only evident underSEM ex- choanosomalskeleton displays a diffusearchitec-
amination (Fig. lg, PI. Ilia). The spicules are ture. Tracts of oxeas show a vague radialpattern
17-22/xm intheiroverall length, withactinesmea- from the inner choanosome up to the ectosome,
suring 6—10/xminlength. They are veryabundant. protruding in long hispidating tufts atthe inhalant
Amphiasters are very rarely transformed into zones. Calthrops are abundant everywhere in the
sanidasters or metasters (Fig. If). choanosome, butno special spatial organization is
Plesiasters: with usually 3-5 actines covered by apparent.
microspines (Fig. lh; PL Illb). Actines are 10-15 Dichotriaenes and mesodichotriaenes are more
/xm in length. They are very scarce. abundantin the inner choanosome, incontrast to
the general pattern of the Astrophorida (Solías,
Skeleton: 1888). Streptastersare denselyscatteredeverywhere
Spicules are densely arranged, providing a hard in the choanosome.
134/III M. Maldonado- Taxonomicsignificance ofthe mesotriaene in Astrophorida
Plate III.Microscleres: (a)amphiaster,(b)plesiaster,(c)reduced streptaster, (d) oval microstrongyle.
Distribution. - Known only from the coasts of however, this interesting species hasbeen disguised
PortugalbetweenFaroandSines(Von Lendenfeld, foralong timedueto severalconsecutive systemat-
1894)and thecoasts ofGalicia(present record), at ic interpretations: (1) Von Lendenfeld(1903) ex-
a depth of 300 m. Specimens with mesodichotri- plicitly defined the genus Pachastrella as Pacha-
aenesmentionedby Topsent(1902) underthename strellidae without mesotriaenes (p. 73), although
ofPachastrellaabyssi mightactually correspond to he paradoxically includedinthesamepaper(p. 75)
Pachastrellaovisternata, but dataabouttheir loca- a description of P. ovisternata, underlining the
tion wereomittedby the author. presence of characteristic mesodichotriaenes.(2)
Later,P. ovisternatawasclaimedajuniorsynonym
of Pachastrella monilifera by Topsent (1902: 14;
Taxonomicdiscussion
1904:93, 94). The systematic valueofthe mesotri-
The collected specimen completely fits the holo- aenes at specific level was consideredlow by Top-
type of Pachastrella ovisternata. Unfortunately, sent, whoassumedthatthese spicules occasionally
Bijdragen tot deDierkunde, 63 (3) - 1993 135
appeared in Pachastrella from sporadic modifica- + P. abyssi) as proposed by Topsent (1902,
tions in dichotriaenes which originated, in their 1904). Consequently, PachastrellaovisternataVon
turn, from occasional modifications in calthrops Lendenfeld, 1894is herein claimedas a valid spe-
(Topsent, 1902, 1904). (3) The disregardofthe sys- cies, clearly different from P. monilifera.
tematic significance of the mesotriaenes which Itis also worthnoting thatP.ovisternataresem-
emerged from Topsent's interpretations brought bles the Indian species Yodomiaperfecta Dendy,
Ferrer-Hérnandez(1914) to incorrectly record the 1916, which has a spicule complement of long
name of P. ovisternata for specimens lacking oxeas, mesotriaenes, calthrops, amphiasters, mi-
mesotriaenes, dichotriaenesandcharacteristiclong crorhabdoid streptasters ("reduced streptasters"
oxeas. After re-examination, I came to the con- according to Dendy, 1916), and oval micro-
clusion that the material described by Ferrer- strongyles. Y. perfecta is only differentiatedfrom
Hernández (1914) actually belongs to the species P. ovisternatainminor detailsofits skeleton, such
Pachastrellamonilifera. as the absence of dichotriaenesand the occurence
The illegitimacy ofP. ovisternatahas beensup- of tetracladose mesotriaenes in addition to the
ported for a long time mainly because of a vague dichotomous ones.
report on specimens bearing dichotriaenes and The genus YodomiaLebwohl, 1914,erected for
mesodichotriaenes. These specimens were at first Yodomiaijimai,was modifiedby Dendy (1916) in
regarded by Topsent (1902: 14, 17)as "peculiar" orderto includeasecondspecies, Yodomiaperfec-
materialbelonging to P.abyssiSchmidt, 1870,but, ta. Both species appear to be veryrare, since they
two years later, Topsent himself (1904) claimed have beenrecorded only once (Sea of Japan: Leb-
synonymy ofP. abyssi and P. monilifera. Meso- wohl, 1914) and twice (Indian Ocean -Saya de
dichotriaenes were envisaged by Topsent (1902, Malha-:Dendy, 1916; Burton, 1959),respectively.
1904) as spicules ofsporadic occurrence, i.e. occa- Some skeletal features of Y. ijimai, such as the
sional results of haphazard modifications in cal- presence of long-shafted triaenes(rhabdome mea-
throps and thusof no systematic value. suring up to 2200 /¿m and undeveloped clads),
In contrast, most evidence indicatesthat meso- mesotriaenes with undivided clads, absence of
dichotriaenesof P. ovisternata are a well estab- microrhabdoidstreptasters,andpresenceofcurved
lishedcategoryofspicules: (1) Theyare always per- microstrongyles with occasional oxeote ends(pre-
fect inshape (PI. lie, d), while the occurrence of sumably arising from microxeas and non-homolo-
somemalformationswouldbeexpected underTop- gous with the oval microstrongyles), suggest that
sent's assumption. (2) Inaddition, a greatvariabili- this species is not closely relatedto Y.perfecta. In
ty in size occurs inthecalthrops whereas thesize is contrast, Y. perfecta and P. ovisternataare noted
especially uniform inthe mesotriaenes.(3) Thear- to be very closely related, in spite of having tradi-
rangementofmesotriaenesinthe sponge is differ- tionally belonged to differentgenera.
ent to that ofthecalthrops. Mesodichotriaenesare Ina discussionontherelationships concerning P.
particularly confined to the inner choanosome, ovisternata, the monospecific genus Brachiaster
whereas calthrops indiscriminately occur every- Wilson, 1925, characterized by the presence of
where inthesponge. (4) Finally, there are no other mesotriaenes transforming to desmas, can not be
reports on specimens withmesotriaeneseitherinP. obviated. This genus was formerly regarded as a
moniliferaor inP. abyssi (cf. Schmidt, 1870, 1880; lithistid "incertae sedis" (Wilson, 1925), later
Carter, 1876; Solías, 1888; Van Soest & Stentoft, redescribed in Pachastrellidae (Lévi & Lévi, 1989)
1988). Calthrops and mesodichotriaene mega- and recently reclassified into LithistidaTetracladi-
scleres are further compared in PI. lib. na (Levi, 1991). The presence in Brachiaster of
Therefore, the skeletaldifferencesnoted, mainly some skeletal characters also present in typical
the presence of especially long oxeas and meso- pachastrellids, such as diversely branched meso-
dichotriaenes, isolate and identify P. ovisternata triaenes (although becoming desmas), oval micro-
from the remaining complex of species li(fePra. moni- strongylesandmetasters,require careful considera-
136 M. Maldonado- Taxonomic significance ofthe mesotriaenein Astrophorida
tion. In my opinion, and taking into account the Poecillastra-Sphinctrella), to solve the relation-
fact that species such as Yodomiaperfecta and ships among Brachiaster simplex, Pachastrella
Pachastrella ovisternata were overlooked by Lévi monilifera,P. echinorhabdaPulitzer-Finali, 1973,
(1991) inhis discussion about therelationships of P. ovisternata, and Yodomiaperfecta. This multi-
Brachiaster, itwouldbeadvisabletoreconsiderthe ple outgroupconsistedofallfourspecies belonging
possible systematic relocationof this genus inthe to Triptolemus along with Stoeba spp. (defined at
Pachastrellidae. generic level). Sucha heterogeneous set is allowed,
since "theoutgroupcomparisons need notbe con-
strained by nomenclaturalrank or Linnean hier-
Phylogenetic analysis archical structure" (Watrous & Wheeler, 1981).
Theparsimony analysis was seentobe thebest way Taxonomic background
to tackle the obscure relationships between the
above-mentioned species. The study was carried Alltaxaincludedintheanalyses as wellassome dis-
out in three phases. The first phase analyzed the carded taxa are briefly diagnosed and discussed
relationships among the pachastrellid genera, in- below.
cluding Brachiaster.Thesecondphase explored the
possible generic placement oftheproblematic spe- Ingroup genera:
cies, such as Yodomia ijimai, Yodomiaperfecta, Poecillastra Solías, 1888: Pachastrellidae having
and Pachastrellaovisternata. The third phase ex- oxeas, and calthrops, or pseudocalthrops as
amined the relationships between several species megascleres. Microscleres consistofmicroxeasina
traditionally assigned to three different genera single category and several types of streptasters
(Pachastrella, Brachiaster, and Yodomia), based withlong andthin actines. Tetraxonspicules occur
on the results of the preliminary parsimony ana- everywhere inthe choanosome.
lyses. Characella Solías, 1888: Pachastrellidae with a
spicule complement similar to Poecillastra, but
Outgroup selection wheretetraxonsarerestrictedto subectosomalloca-
A multiple outgroup was utilizedin all analyses, tions andtwo categories ofmicroxeasalways occur.
since it is the most stringent test of the ingroup Some authors (e.g., Pulitzer-Finali, 1983; Van
monophyly (Bergquist & Kelly-Borges, 1991). Soest&Stentoft, 1988) doubtthevalidity ofthis ge-
According to the traditional family diagnoses nus, but no complete study has been madein this
(e.g., Lévi, 1973), members of Theneidae could matter. Ihaveexaminedholotypes andmaterialbe-
be thought to be the most appropriate outgroup longing to Characella pachastrelloides and Ch.
for tackling the relationships among pachastrel- tripodaria, noting that the location of tetraxons
lid genera. However, calthropellid and stellet- was always restricted to peripheral choanosome.
tid generawere usedtoelaboratetheoutgroup.The Sphinctrella Schmidt, 1870:Pachastrellidae whose
occurrence of short-shafted mesotriaenes along oxeas are dividedinto two categories according to
withcalthrops insomecalthropellids, as well as the their choanosomal or ectosomal location. Cal-
occurrence of streptasters in some stellettids (e.g., throps or pseudocalthrops are restricted to the
genusStryphnus), were consideredvery useful fea- peripheral choanosome. Microscleres consist of
tures in ascertaining the homoplasous or homolo- oneor several kindsofstreptasters and oneor two
gous nature of such characteristics in Astropho- categories ofmicroxeas.Oscules are grouped inex-
rida. halantareas surroundedby palisades ofectosomal
The samereasoning was applied inthe analysis oxeas.
at specific level and, thus, the subgroup consist- Stoeba Solías, 1888 (sensu Dendy, 1905): Pacha-
ing of Triptolemus-Stoeba was chosen as out- strellidae with calthrops or pseudocalthrops par-
group(rather than the subgroup consisting of tially or completely replaced by short-shafted
Bijdragen tot deDierkunde, 63 (3) - 1993 137
dichotriaenes(as, for instance, in Stoeba extensa feld and Lévi, typical species remaining in this
Dendy, 1905orSt. natalensisBurton, 1926).Oxeas genus in the Atlantic-Mediterranean region are
are absent. Microscleres are exclusively a single Calthropellastelligera(Schmidt, 1868),C.recondi-
typeof sanidasterwith degenerate actines, located ta Pulitzer-Finali, 1973, and C. simplex.
inanectosomallayer. Endolithicor parasitic habit Pachataxa De Laubenfels, 1936: Calthropellidae
characterizesspecies ofthis genus. with calthrops, regular euasters and characteristic
Triptolemus Solías, 1888:ParasiticPachastrellidae aberrant euasters displaying microrhabdoid shape
whose tetraxons are exclusively short-shafted (sometimes named ataxasters). Oxeas are absent.
mesotriaeneswith clads diversely branched. Oxeas Short-shaftedmesotriaenes occur in some species
may be absent in all species (according to Sarà, such as Pachataxa enigmatica Lévi & Lévi, 1983,
1959), since those formerly described in Triptole- butthey areabsentinP. lithistina(Schmidt, 1880)
mus intextus (Carter, 1876) (=T. parasiticus Car- and P. luteaPulitzer-Finali, 1986.
ter, 1876, sensu Levi&Lévi, 1983)and T. cladosus Stryphnus Solías, 1888: Stellettidae whose mega-
Solías, 1888 presumably belonged to the host scleres are long-shafted triaenes andoxeas. Micro-
sponges. Microscleres are streptasters, including scleres consist of euasters as well as streptasters.
degenerate forms in species such as T. cladosus,
(according to Lévi &Levi, 1983: 153), T. simplex Discarded genera:
Sarà, 1959,and T. intextus. Microxeas are present Indeed, it would be interesting to include in the
in the species T. cladosus and T. incertus Kirk- analysis of the pachastrellid relationships some
patrick, 1903. controversial genera(mentioned below), but this
PachastrellaSchmidt, 1868:Pachastrellidaewhose task wouldtaketoo longandwouldcomplicate this
megascleres are oxeas and calthrops or pseu- study enormously. These generaare discussed be-
docalthrops. Microscleres consist of oval micro- low to provide a better understanding of the
strongyles and several kinds of streptasters in- problematic taxonomiebackground.
cluding degenerate forms. The presence of meso- Dercitus Gray, 1867: This genus with toxas and
triaenes in some species, presumably belonging to massive habit, is,inmy personal opinion, different
this genus, is examined further below. from Stoeba. The shape of the microrhabdoid
Brachiaster Wilson, 1925: Monospecific genus microscleres is themain supportfor thetraditional
whose megascleres are styloxeas, short-shafted assumed identity between Dercitus and Stoeba.
mesotriaeneswithcladsdiversely branchedanddes- However, the microrhabdoid shape may be de-
mas with mesotriaene crepis (named mesotriders, ceptive in establishing relationships, since it is a
according to Reid, 1970). Short-shafted dichocal- morphological convergence which may be seen
throps, transforming to desmas, maybe presentor in microxeas (e.g., Characella pachastrelloides),
absent (Wilson, 1925; Lévi & Levi, 1989). Micro- streptasters (e.g., Triptolemussimplex, Pachastrel-
scleres are oval microstrongyles and metasters. laechinorhabda) and even in euasters (e.g., in spe-
cies of Pachataxa: Topsent, 1897; DeLaubenfels,
Outgroup genera: 1936).As faras thepresenceoftoxas is concerned,
Pachastrissa Von Lendenfeld, 1903: Calthropelli- itmust be concededthatthisisanenigmatic feature
daewithoxeas, calthrops, and regular euasters (ac- whose relationship with theremaining microsclere
cording to Von Lendenfeld, 1903; Levi, 1973). types inAstrophorida is unclear; it may be impor-
Short-shaftedmesotriaeneswith unbranchedclads tant from an evolutionary point of view, but it is
are present in some species, such as Pachastrissa uninformativein aparsimony analysis. The alter-
pathologica (Schmidt, 1868) and P. inopinata native taxonomieopinion, viz. bothgenerashould
(Pulitzer-Finali, 1983). be separated, has been postulated previously by
Calthropella Solías, 1888: Calthropellidae with authors such as Dendy (1905), Burton(1926), and
calthrops and regular euasters. Oxeas are absent. Vacelet & Vasseur (1971), whereas most contem-
Aftertheapplication ofthecriteriaofVon Lenden- porary authors donot make such a generic distinc-
138 M. Maldonado- Taxonomicsignificance ofthe mesotriaenein Astrophorida
Table I.General datamatrix. Lowercaseletters indicate character states,positivesymbols (+)indicate taxa included in each analysis,
negativesymbols (-)correspondtotaxa and/or characters notused intheanalyses. Characters 1-11 wereused intheanalyses atthe
genericlevel and characters2, 4,5,9, 10, 12-16 in the analyses atthe specific level. For explanationofthe characters, seetext.
OTUS CHARACTERS TREES
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Tl T2T3 T4
STRYPHNUS abbaac bbaaa - — — — — + +
PACHASTRISSA a b a b aba a b a a d - — — — — + +
PACHATAXA a a a ababa a c a a d - — —
CALTHROPELLA aaabaaabaad — —
POECILLASTRA ababaabbabac - — — — —
CHARACELLA a b b b a abb a be a c - — —
SPINCTRELLA a c b b a a b a be a c - — - —
STOEBA baabaacaaaacaabc + + + +
TRIPTOLEMUS b aba a b a bda aba ac - — — — — + + + —
PACHASTRELLA - 1 ababaadaabb
PACHASTRELLA - 2 a b a b aba d a a b b
BRACHIASTERsimplex abaabc abaabbac baa + + + +
YODOMIA ijimai ababbebdeae
Yodomiaperfecta ababbadaabbabc bba - + — +
Pachastrella ovisternata ababbadaabbabbba - + - +
Pachastrella monilifera -b - b a - -- a b - a a b b a — — - +
Pachastrella echinorhabda — b - ba — - - a b — babe a — — — +
Triptolemussimplex -a — a b - — — a a — c c c b b --- +
Triptolemusintextus - ? — a b — — — a a -ccbbb--- +
Triptoleusincertus — a - ab - -- ba - ccbaa - — — +
Triptolemuscladosus - ? — a b - — - b a - c c bba — — — +
tion. Both opinions are debatableand itis obvious ciesAcanthotriaenacriptaVacelet, Vasseur&Lévi,
thatthis systematic matter is far from being com- 1976. The spicule complement consists of acan-
pletely solved. In any case, the eliminationofthis thodichotriaenes, spirasters, rhaphides and per-
genusfrom thepresentanalysis wasthought advisa- haps, small oxeas. In spite of being formerly
ble soastoavoidfurthercomplications, as ithardly described in the Pachastrellidae, the relationships
affects either the aims or the conclusions of this betweenthis genusandtheremaining pachastrellids
study. analyzed here are veryobscure.
Lamellomorpha Bergquist, 1968:Monospecific ge- NetheaSolías, 1888:Artificialgenuserectedtocon-
nus erected for Lamellomorpha strongylata Berg- tain species having calthrops with underdeveloped
quist, 1968andlocatedbytheoriginalauthorinthe actines. It was rejected in Lévi's classification
dustbinorderEpipolasida. Themegasclere comple- (1973) and questioned by other authors (e.g.,
ment lackstetraxon spicules andconsists exclusive- Pulitzer-Finali, 1983). In my opinion, this genus
ly of flexuous strongyles. Microscleres are two ought to be formally abandonedand its species
kinds of degenerate (microrhabdoid) streptasters reclassified in other pachastrellid genera: Nethea
along withamphiaster-metaster forms having well- nana(Carter, 1880)and N. amygdaloides (Carter,
developed actines. Such microscleres could cor- 1876) clearly belong to the genus Poecillastra;
respond toa very modified pachastrellid, but for Nethea dissimilis Sarà, 1959 probably belongs to
thepresentthe genusis excludedfromthe analysis the genus Stoeba.
dueto its uncertainstatus.
Acanthotriaena Vacelet, Vasseur & Lévi, 1976: Characteranalysis
Monospecific genuserected for theenigmatic spe- A totalof sixteen characters were used in the dif-
