On Triassic Murchisonia -like gastropods—surviving the end-Permian extinction to become extinct in the Late Triassic

Nützel


Introduction
High-spired gastropods with selenizone (slit-band, closed shell slit) are a typical component of Paleozoic gastropod faunas from the Ordovician onwards.Like many typical Paleozoic gastropod groups, they were severely affected at the end-Permian mass extinction (Erwin 1990;Nützel 2005;Karapunar and Nützel 2021) and became a minor element in the Triassic until their demise in the Late Triassic.Due to their rarity in most of the Triassic faunas, studies on Murchisonia-like gastropods from the Triassic are scarce and the Triassic representatives of the group are less known compared to their Paleozoic representatives.Herein, we revise Triassic Murchisonia-like gastropods to better understand the diversity of this group in the Triassic and their possible relationships to Paleozoic forms.
High-spired slit-bearing gastropods have been traditionally assigned to the family Murchisoniidae or to the superfamily Murchisonioidea (e.g., Knight et al. 1960) and many of such gastropods ranging from the Ordovician to the Triassic were placed in the genus Murchisonia.However, there is a considerable number of Murchisonia-like genera and the composition of the group is quite complex.Murchisonia-like gastropods are considered either as exceptionally high-spired Pleurotomariida (Vetigastropoda) or as slit-bearing Caenogastropoda depending on the larval shell morphology and shell microstructure (Koken 1889;Knight et al. 1960;Nützel 1998;Nützel and Bandel 2000; see also Mazaev 2011).However, these characters are still unknown for many genera and hence their classification is doubtful.Murchisonia, the type genus of the group, has a Devonian type species, M. bilineata (Dechen, 1832), which is a highly variable species (Heidelberger 2001;Heidelberger and Koch 2005).Its early ontogeny, including protoconch morphology, is largely unknown and this hinders a correct taxonomic and systematic assessment of Murchisonia and Murchisoniidae in general.Several late Paleozoic Murchisonia-like gastropods (Goniasmatidae) have been reported with well-preserved early ontogenetic shells possessing caenogastropod-type larval shells (Yoo 1988(Yoo , 1994;;Nützel 1998;Nützel and Bandel 2000;Bandel 2002;Bandel et al. 2002;Pan and Erwin 2002;Nützel and Pan 2005;Karapunar et al. 2022).The specimens from the Pennsylvanian Buckhorn Asphalt deposit (USA, Oklahoma) further revealed that their Carboniferous representatives lack nacre but have an aragonitic crossed lamellar shell microstructure (Bandel et al. 2002).The absence of nacre supports a placement of these gastropods in Caenogastropoda because vetigastropods including Pleurotomariida commonly possess nacre, and only some vetigastropods are known to lack nacre (e.g., Skeneidae, Fissurelloidea; Ponder et al. 2020).By contrast, nacre is unknown in Gastropoda outside Vetigastropoda.As already stated by Koken (1889), Murchisonia-like gastropods commonly develop an anterior siphonal canal, a character that is absent in true Pleurotomariida.This character also brings the entire group closer to caenogastropods.On the other hand, Frýda and Manda (1997) and Frýda et al. (2008) documented well-preserved Murchisonia-like gastropods that have a protoconch typical of Vetigastropoda (i.e., consisting of about one whorl) suggesting placement in Vetigastropoda.The presence of nacre in the Ordovician "Murchisonia" (Mutvei 1983) further corroborates such a placement at least of early members assigned to this group.Murchisonioidea, in its present composition, is likely polyphyletic and holds members of both, Vetigastropoda and Caenogastropoda.There is no modern phylogenetic analysis including shell microstructure and larval shell characters of Murchisonia-like gastropods; hence, the importance of these characters in inferring the phylogeny of Murchisonioidea are not yet assessed.
There are several Triassic holdovers of high-spired, selenizone-bearing gastropods.To date, six of these Murchi so nia-like genera comprising a total of 30 nominate species have been reported from the Triassic: "Murchisonia", Pseu do murchisonia, Cheilotomona, Trypanocochlea, Wan neri spira, and Vistilia.Batten (1973) and Hallam and Wig nall (1997) stated that Murchisonioidea became extinct at the end-Triassic mass extinction event.Based on new material and the re-study of type material of several species, we discuss the diversity of Triassic Murchisonia-like gastropods, their link to late Paleozoic taxa, and revise their classification.

Systematic palaeontology
Subclass Caenogastropoda Cox in Knight et al., 1960 Family Goniasmatidae Nützel andBandel, 2000 Included genera: Laschmaspira Mazaev, 2003, andAltadema Kues, 2002; these genera have been placed in Orthonematidae.However, they clearly possess a selenizone and hence they are placed in Goniasmatidae.Pseudomurchisonia Koken, 1896, has only a weak sinus in the upper whorl portion; it is possible that it would develop into a selenizone.Therefore, it is tentatively placed in Goniasmatidae.Murchisonietta Nützel, Kaim, and Grădinaru, 2018, a subjective younger synonym of Wortheniopsis Böhm, 1895, has also been placed tentatively in Goniasmatidae (Nützel et al. 2018).
Description.-Shellhigh-spired; holotype consists of about 9 whorls, 15.4 mm high, 7.9 mm wide; first four whorls smooth, convex, dome-shaped with an apical angle of 70-80°; initial whorl 0.33-0.36mm wide; clear ontogenetic boundaries (embryonic/larval/teleoconch) not visible due to preservation or possibly gradual; later teleoconch with an apical angle of ca.30°; teleoconch whorls markedly convex, angulated at borders of selenizone, with a broad ramp; selenizone forming from third whorl onwards as an increasingly deepening sinus of growth lines; selenizone on mature whorls broad, concave with lunulae of dense, distinct growth lines; late teleoconch whorls with numerous, distinct spiral lirae above and below selenizone; suture deep; base convex, anomphalous, demarcated from whorl face by an angulation, with numerous spiral threads.
Remarks.-The most similar Triassic species is Laschmaspira euglypha (Koken, 1896), from the same locality (Feuerkogel).However, this species lacks spiral ornament, its whorls are more angulated, and the selenizone starts after the first whorl according to Koken (1896Koken ( , 1897)).Laschmaspira lirata sp.nov.exhibits a marked ontogenetic change regarding apical angle and ornament from broad, smooth, slitless initial whorls to ornamented much more slender and slit-bearing later whorls.However, a clear indication of a larval shell of the planktotrophic type could not be found.The size of the initial whorl (>0.3 mm) is rather large and suggests non-planktotrophic larval development (see Nützel 2014).Laschmaspira li rata sp.nov.can be regarded as a descendant of Paleozoic Goniasmatidae.The Permian Goniasma gerasimovi Mazaev, 2019, resembles Laschmaspira lirata sp.nov. in having an ornament of numerous spiral lirae which is otherwise unusual for Goniasma.However, G. gerasimovi differs in having a submedian angulation as is typical for Goniasma.
Stratigraphic and geographic range.-Typehorizon and locality only.
Remarks.-Pseudomurchisonia was tentatively placed in Purpurinidae (Caenogastropoda) by Wenz (1939: 526) who erroneously considered P. woehrmanni Koken, 1896, to be the type species.Thus, the genus was not included in the Treatise (Knight et al. 1960) which covered only few caenogastropods.Both originally included species, Pseudomurchisonia insueta Koken, 1896, andP. woehrmanni Koken, 1896, come from the Carnian (Upper Triassic) of the Feuerkogel in Austria.Both are moderately high-spired and have a broad selenizone that appears late during ontogeny.Apart from the two originally included species, two Early Triassic species were placed in Pseudomurchisonia: P. extracta (Berger, 1860) and P.? sundaica Krumbeck, 1924, but none from the Paleozoic and the post-Triassic.
The type species Pseudomurchisonia insueta (see below) differs from Goniasma in lacking an angulation, but resembles this genus in having a selenizone low on the whorls and lacking strong ornament.We therefore place this genus tentatively in Goniasmatidae.More knowledge about the early ontogeny of Pseudomurchisonia insueta is needed for a better substantiated systematic placement of this genus.
Pseudomurchisonia extracta (Berger, 1860) (originally placed in Natica) is based on an obviously poorly preserved specimen (probably a steinkern) from the Schaumkalk, a lithological unit of the Muschelkalk in the German Basin.The type is therefore of Anisian age.It shows a markedly gradate spire with a ramp bordered by an edge high on the whorls.This species has been placed in Pseudomurchisonia by Wittenburg (1908a: 284, pl. 5: 7) who illustrated a specimen with evenly rounded whorls and a median selenizone from the Werfen Formation of the Valsugana, Italy.Wittenburg's (1908a) specimen is certainly not conspecific with Bergers's (1860) type specimen.The Early Triassic specimen reported by Wittenburg (1908a) could either be a member of Pleurotomariida or Goniasmatidae.Baumgarte and Schulz (1986) and Kramm (2004) placed Pseudomurchisoni extracta in Angularia; their illustration of specimens from Hessen indicates that this assignment is more correct.Pseudomurchisonia extracta is probably a nomen dubium but its type specimens must be studied.
Pseudomurchisonia? sundaica Krumbeck, 1924, from the Lower Triassic is actually close to the type species Pseudo murchisonia insueta Koken, 1896, and could be congeneric.Remarks.-Weillustrate a single specimen (teleoconch fragment) from the Carnian of the Feuerkogel, Austria, representing the type species Pseudomurchisonia insueta, housed at the NHMW.The spire whorls are convex with an edge low on the whorls that is reduced later on.The earliest preserved whorl has neither a sinus nor a selenizone but straight, slightly opisthocyrt growth lines.Then a sinus and eventually a selenizone develops distinctly below mid-whorl.The selenizone is flush with the whorl face and smooth with sinuous growth lines.The whorls are smooth except of comarginal furrows in some whorls.The base is strongly convex and anomphalous.The transition from whorl face to base is evenly rounded.
The present specimen agrees well with the description and illustrations of Pseudomurchisonia insueta as given by Koken (1896Koken ( , 1897)).The apical whorls including the protoconch and the shell microstructure are unknown.Hence the higher classification of Pseudomurchisonia is doubtful.As already noted by Karapunar and Nützel (2021)
Remarks.-We place the subfamily Cheilotomoninae in Goniasmatidae due to their high-spired shell with a median selenizone.Species with a multi-whorled protoconch of the planktotrophic type with sinusigera or a paucispiral protoconch with sinusigera (characteristic of goniasmatids) have not been documented in the members of Cheilotomoninae.Cheilotomona has smooth early whorls with fluent transition to the teleoconch and a large initial indicating non-planktotrophic early ontogeny (Karapunar and Nützel 2021, and see below).
Cheilotomona, Trypanocochlea, and Vistilia were previously placed in Murchisoniidae but Murchisonia lacks a prominent whorl crest on which the selenizone is situated, and this brings these genera close to Goniasma and thus they are placed in Gonismatidae.The protoconch of Trypanocochlea cerithioides is unknown and therefore, the possibility that Trypanocochlea belongs to Pleurotomariida and not to the caenogastropod family Goniasmatidae cannot be excluded.On the other hand, general whorl morpho logy, surface orna- ment (subsutural cord and strong axial ribs), and early ontogenetic shell development (nodular periphery, subsutural cord) supports its close association to Cheilotomona.Nützel and Nakazawa (2012) showed that a Permian Trypanocochlea species from Japan has a mammilated protoconch of the caenogastropod type supporting a placement in Goniasmatidae.
Remarks.-As previously stated by Karapunar andNützel (2021), Schnetzer's (1934) original assignment to Stuorella cannot be maintained because this genus does not have a whorl angulation with a convex selenizone.Instead, Stuorella has a selenizone on flat whorl face somewhat above basal edge of the whorls.Vistilia salisburgensis has the characteristic teleoconch morphology of Vistilia with low whorls.However, protoconch and early teleoconch of Vistilia salisburgensis are unknown.Vistilia salisburgensis closely resembles Cheilotomona tristriata (Münster, 1841) from the lower Carnian St. Cassian Formation (Karapunar and Nützel 2021: fig. 86) in general whorl morphology, surface ornament and in having a pronounced subsutural spiral cord.The presence of a single subsutural cord is a feature also shared by Cheilotomona (Fig. 4) and Trypanocochlea (Fig. 6).Vistilia salisburgensis is the oldest known Triassic species of this genus.Vistilia last appeared in the Carnian (Koken 1896).
Stratigraphic and geographic range.-Knownfrom the type locality only, see above.
Trypanocochlea cerithioides (Koken, 1896)  Description.-Shellhigh-spired, apical angle ca.45°; type specimen consists of ca. 8 whorls, 7.8 mm high, 3.4 wide; earliest preserved whorls rounded, smooth, developing an angulation low on whorl face after one-two whorls; whorl face strongly angulated slightly below middle of whorl face; selenizone broad, situated on angulation, forming periphery; selenizone forms late (after the second preserved whorl), ornamented with pronounced node-forming lunulae, and a median spiral cord; lunulae closely spaced in early whorls, widely spaced in later whorls; selenizone bordered by outward bending shell forming sharp edges (spiral cords); whorl face steeply sloping above selenizone, ornamented with strengthened growth lines and spiral thread in subsutural zone; whorl face below selenizone sharply inclined adaxially; transition from whorl face to conical, convex base demarcated by spiral cord, accompanied by one or few spiral threads; aperture trapezoidal; inner lip convex with about 12 spiral lirae (folds).
Remarks.-Trypanocochlea cerithioides, type species of Trypanocochlea, is a murchisonimorph gastropod with a strongly ornamented, convex selenizone.Its inner lip has spiral lirae (folds) unlike any other members of Goniasmatidae.A middle Permian representative of Trypanocochlea, has been reported by Nützel and Nakazawa (2012) but that species seemingly lacks folds on the inner lip (maybe due to preservation).Similar gastropods (also lacking folds on the inner lip) have also been reported from the Pennsylvanian/lower Permian of the USA: Taosia crenulata (Girty, 1939) (Kues 1991(Kues , 2004a, b), b).Taosia crenulata differs much from the type species of Taosia, and at first glance this late Paleozoic species resembles Trypanocochlea.However, while the selenizone of Taosia crenulata is situated on upper whorl face above the nodular periphery, the selenizone of Trypanocochlea cerithi oides is situated on the angular periphery and the nodes are formed within the selenizone.Cheilotomona subgranulata (Klipstein, 1844) from the St. Cassian Formation develops similar nodular selenizone on whorl periphery, but species of Cheilotomona lack the folds on inner lip.The only other report of Trypanocochlea (an unnamed species) is from the ?upperNorian/Rhaetian (Upper Triassic) of Peru by Haas (1953), who reported absence of folds in the Peruvian species.Due to the unclear age if this probably last occurrence of Trypanocochlea, the exact timing of the exticntion of this genus is unknown.
Stratigraphic and geographic range.-Knownfrom the type locality only, see above.
Remarks.-The type species of Altadema has a small, moderately high-spired largely smooth shell with strongly convex whorls; its selenizone is situated high on whorl.So far, four Pennsylvanian species have been assigned to this genus (Kues 2002;Mazaev 2003).Herein, we place the Early Triassic species Altadema kokeni (Wittenburg, 1908a) and Altadema hausmannae sp.nov. in Altadema.Altadema haus mannae has a broad slit-band above the periphery in mature whorls whereas Altadema kokeni (Wittenburg, 1908a) has a sinus or selenizone high on the whorls.Material.-Typematerial; in addition numerous specimens in rock-forming quantities.
Description.-Largestspecimen comprises ca.six whorls (apex missing), 4.9 mm high, 3.0 mm wide, turbiniform with variable apical angle of ca.60-80°; whorls markedly convex, separated by distinct sutures; whorls with more or less pronounced subsutural shelf so that spire is gradate in most specimens; shell smooth (but studied specimens covered by a reddish crust of iron oxides or hydroxides that may obscure ornament if ornament was present); ramp demarcated by the adapical edge of broad selenizone; transition from ramp to lateral whorl face may be angular; selenizone situated high on the whorls; base convex with an umbilical chink; transition from whorl face to base evenly rounded.
Remarks.-Altadema hausmannae sp.nov.occurs in rockforming quantities at its type locality (Nützel and Schulbert 2005).Nützel and Schulbert (2005) identified this species as Pseudomurchisonia kokeni Wittenburg, 1908a (also from the Lower Triassic Werfen Formation) but a closer examination of the holotype of P. kokeni reveals that they are not conspecific (see below).Altadema kokeni has only a slight sinus, not a selenizone.Otherwise both species resemble each other closely.Altadema hausmannae differs widely from the type species Pseudomurchisonia insueta in whorl morphology and position of selenizone.The other species of Altadema (A. convexa Kues, 2002, A. cryptocarina Mazaev, 2003, A. altadema Mazaev, 2003, A. cryptocarina Mazaev, 2003, and A. lira Mazaev, 2003, all Pennsylvanian) are more slender and the spire is less gradate (having a larger angle between sutural shelf and outer whorl face).
Stratigraphic and geographic range.-Knownfrom the type locality only, see above.
Description.-Theholotype comprises about four whorls, is 4.8 mm high and 3.5 mm wide.It is turbiniform with an apical angle of ca.65°.The whorls are markedly convex and separated by deep sutures.The shell is smooth and shiny except for fine growth lines.The growth lines are oblique prosocline below the adapical suture, form a shallow sinus above the periphery and almost orthocline prosocyrt between periphery and abapical suture.
Remarks.-The preservation is good when compared with the otherwise mostly poor preservation of the Werfen gastropods.The shell is replaced by a sparitic, slightly reddish calcite.The specimen is embedded in a hard calcareous rock.
It is therefore likely that it comes from the gastropod oolite because other fossiliferous rocks of the Werfen Formation are usually more marly.It resembles Altadema hausmannae sp.nov. in general shape and by having a smooth shell, but it lacks a true selenizone; instead it has a sinus high on the whorls.It is possible that this specimen represents a juvenile shell and that a selenizone would develop later during ontogeny.
Stratigraphic and geographic range.-Knownfrom the type locality only, see above.
Emended diagnosis.-Shellmoderately high-spired to fusiform; whorls evenly rounded or weakly angulated; whorls embracing somewhat below periphery; surface smooth or with spiral ornament; sinus or shallow slit high on whorl face, which may form a weak angulation; sinus/slit appears very late in ontogeny.
Remarks.-Wortheniopsis was erected by Böhm, 1895, for Worthenia-like shells (placed in Pleurotomariidae) lacking prominent shell angulations.The growth lines are not well-preserved or documented for the type species W. mar garethae and hence the presence of a slit-band (selenizone) was only assumed by Kittl (1894) and Böhm (1895).We studied material from the Marmolada Limestone (Figs. 9, 10) and found that Wortheniopsis margarethae (Fig. 9) lacks a true selenizone (slit-band).Instead, growth lines have a backwards projection above mid-whorl of mature whorls forming a shallow sinus.The same pseudo-selenizone has been reported for the Anisian genus Murchisonietta Nützel, Kaim, and Grădinaru, 2018 (Fig. 11) and therefore we consider Wortheniopsis and Murchisonietta to represent synonyms.Similar to Altadema kokeni, Wortheniopsis also develops a sinus high on the whorls in late ontogeny.At this point, the higher classification of Wortheniopsis is unclear because it lacks a true selenizone, its shell microstructure and early whorls including protoconch are unknown.Wenz (1938: 128) included Wortheniopsis in Pleurotomariidae and Lophospirinae.Knight et al. (1960) placed relatively high-spired taxa (but not as high as murchisoniids) including Wortheniopsis in the murchisonioid family Plethospiridae, which composes taxa ranging from the Ordovician to lower Carboniferous (for instance Platyzona, formerly included in Plethospiridae is regarded as Goniasmatidae, see Karapunar et al. 2022) and is likely a not monophyletic group in its current composition.Nützel et al. (2018) placed the Middle Triassic Murchisonietta (which is considered a junior synonym of Wortheniopsis herein) tentatively in Goniasmatidae and at present, we maintain this arrangement.We consider Wortheniopsis to represent Caenogastropoda, close to Goniasmatidae, but more evidence for that placement is needed, especially from early ontogenetic shell morphology.
There are many erroneous attributions of Permian and Jurassic species to Wortheniopsis.
Description.-Shellmoderately high-spired, apical angle ca.60°; early whorls not well-preserved but earliest whorls seem low trochospiral; whorls distinctly convex, ornamented with strong, densely spaced axial ribs and few spiral cords; axial ribs become knobby when crossing spiral cords in lower part of whorls; axial ribs become visible on third whorl where they are straight prosocline; selenizone appears within 4 th whorl, high on whorl face, flush to slightly concave with strong lunulae; in addition, selenizone has a fine ornament of converging spiral threads (so far unknown from this species); base convex with strong spiral cords and axial ribs with small and axially elongated nodes at intersections.
As has been elaborated in the introduction of this contribution, several of these Murchisonia-like gastropods proved to represent caenogastropods based on their protoconch morphology, the absence of nacre, their high-spired shape, and the presence of siphonal canals.We have shown that this group of caenogastropods apparently survived the end-Permian mass extinction event.On the other hand, high-spired Pleurotomariida were also present in that period of time (Karapunar and Nützel 2021) and Acutitomaria is shown as being a Late Triassic example for that.
Triassic Murchisonia-like gastropods are a small but heterogeneous group as our study has shown.Previously, Triassic murchisonimorph species have been attributed to the genera Murchisonia, Pseudomurchisonia, Cheilotomona, Trypanocochlea, Wannerispira, and Vistilia.We add the genera Laschmaspira, Altadema, and Wortheniopsis (alias Murchisonietta) (Table 1).Trypanocochlea, Wannerispira, Laschma spira, and Altadema originate in the Paleozoic and persist into the Triassic.Pseudomurchisonia, Wortheniopsis, Cheilotomona, and Vistilia are restricted to the Triassic.However, the four Triassic species assigned to Murchisonia (M.euglypha Koken, 1894, M. sera Böhm, 1895, M. sub euglypha Krumbeck, 1924, andM. timorensis Krumbeck, 1924) likely do not represent this genus.Murchisonia eugly pha Koken, 1894, is likely a member of the Laschmaspira (see above), Murchisonia sera Böhm, 1895, is a very slender, small form with a median slit-band and a pronounced ornament of spiral cords.It certainly does not belong in Murchisonia.Its generic assignment needs to be revised, it possibly represents Stegocoelia or an undescribed genus.Murchisonia timorensis also strongly deviates from the type species of Murchisonia, as does M. subeuglypha that as a strong angulation low on the whorls and additional strong spiral cords.
The Triassic Wortheniopsis lacks a true slit-band and have instead a more or less pronounced sinus.Therefore its assignment to Goniasmatidae is tentative; it might represent a new caenogastropod family.
Thus, at the generic level, there seems to be a considerable turnover in Murchisonia-like gastropods at the Paleozoic/ Mesozoic transition according to the current state of knowledge.At the family level, it seems that only Goniasmatidae survived into the Triassic.Murchisonia-like gastropods have been reported from the Lower Triassic to the Norian but no clear Rhaetian species have been identified (species from the Carnian/Norian of Timor need a better dating; commonly only "Late Triassic" is given as age in the literature) and representatives are absent in the Jurassic.Amongst Murchisonialike gastropods only Trypanocochlea has been considered Fig. 12. Pleurotomariid vetigastropod Acutitomaria woehrmanni (Koken, 1896) "Unterer Rötelstein", according to Koken (1896Koken ( , 1897)), Feuerkogel, Austria is given as locality.A. GBA 1897/003/0001, fragmented lectotype, early whorls in lateral view (A 1 ), detail of whorl face in lateral view showing ornament, selenizone with lunulae and converging micro-ornament (A 2 ), early whorls in oblique lateral (A 3 ) and apical (A 4 ) views, last whorl in lateral views (A 5 , A 6 ).
by Ferrari and Hautmann (2022) who restricted their analysis of gastropod diversity to genera from the Norian to the Pliensbachian.They found that the number of genera declined considerably at the Triassic/Jurassic boundary.The standing gastropod diversity declined considerably from the Carnian to the Rhaetian and was very low in the Rhaetian (Nützel 2005;Karapunar and Nützel 2021).Murchisonia-like gastropods are absent in all important Rhaetian faunas with the possible exception of Trypanocochlea sp. from the Pucará Group, Peru.The single specimen in question is from Lot 48, and Haas (1953: 307) indicated that this lot has an age from the "Late Norian or Early Rhaetian" to the Rhaetian, thus it is unclear whether that specimen has a Norian or Rhaetian age.Generally, there are only few species-rich Rhaetian gastropod faunas (e.g., Haas 1953;Nützel and Senowbari-Daryan 1999;Nützel et al. 2022).It is well possible that most of the Murchisonia-like gastropods became extinct at the mid-Carnian crisis (Carnian Pluvial Event) and were thus already extinct prior to the end-Triassic event.Slit-bearing vetigastropods (Pleurotomariida) were also selectively affected by the mid-Carnian crisis (Karapunar and Nützel 2021).

Conclusions
Murchisonia-like caenogastropods, chiefly Goniasma tidae, were diverse and abundant until the Permian, barely survived the end Permian extinction, regained a certain generic diversity within the Triassic with the evolution of several new genera but failed by far to regain their Permian generic diversity.Thus, this once successful and diverse group shares a similar fate (surviving the end-Permian extinction, a reduced Triassic diversity and extinction during Late Triassic crises) as conodonts, orthoceratids, conulariids, and others.This diversity pattern does not qualify for the "Dead Clade Walking" phenomenon i.e., the extinction shortly after a major mass extinction event (survival without recovery) as outlined by Jablonski (2002) because they have survived for ca.30 Ma (at least until the Norian) and even produced a number of new genera.Among gastropods bellerophontids would be a typical example for "Dead Clade Walking", they survived the end-Permian extinction but eventually became extinct within the Early Triassic, at the end of the Smithian (Kaim and Nützel 2011).In both cases, bellerophontids and Murchisonialike gastropods, the marginalization at end-Permian extinction event increased the vulnerability of the groups and likelihood for subsequent complete extinction.Both groups are slit-band gastropods and their dwindling that is accentuated by extinction events is part of a long-term overall decline of slit-band gastropods (see also Karapunar and Nützel 2021).Obviously, there prevailed a long-term selective trend against the character "shell-slit".It is likely that Goniasmatidae and similar forms are related to the ancient caenogastropod clade Cerithioidea (e.g., Nützel 1998;Nützel and Pan 2005) and in so far, this evolutionary lineage still persists until today but this once successful group has ceased at the genus-and family-level.The elimination of shell slits in caenogastropods probably also reflects an evolutionary change of the ventilation of the mantle cavity in these caenogastropods.The exhalant flow went in a lateral or dorsal direction in Murchisonialike caenogastropods and that changed to a more ventral or posterior direction in modern Cerithioidea.
and as discussed below, Acutitomaria woehrmanni (the other species originally included in Pseudomurchisonia by Koken 1896) clearly does not represent the Pseudomurchisonia.Stratigraphic and geographic range.-Carnian(Upper Trias sic), Feuerkogel, Austria.