Our analysis was based on sequence data from taxa in seven of the eight families that Bouchet et al. (2017) assigned to Punctoidea, but coverage was not equal for all families (Table 1). Charopidae, Discidae, Oreohelicidae and Punctidae were each represented by multiple samples. Just under half the sampled species belong to Charopidae, with three of the presently recognized subfamilies being represented, namely Charopinae, Otoconchinae and Rotadiscinae Baker, 1927. Cystopeltidae and Endodontidae were represented by just one species each. Helicodiscidae was represented by GenBank data only (DNA extraction from additional helicodiscid specimens that we procured was unsuccessful). In any event we achieved relatively broad coverage for our ingroup, which included 53 species and 56 terminal branches (as there are three species each represented by two individuals).

After selection through Gblocks, our resulting concatenated alignment was 2196 bp long, with 1176 variable characters of which 935 were parsimony informative. Gblocks maintained 683 bp in the COI fragment, 387 bp in the 16S, and 1126 bp in the IT2+28S. We were unable to obtain high-quality 16S sequence data for four species (Table 1).

The BI and the ML analyses returned nearly identical trees, so we present here the Bayesian phylogeny only (Fig. 1, but also including the ML support values). The ML tree had some minor differences regarding the placement of the charopid taxa Allodiscus Pilsbry, 1892, Chalcocystis Watson, 1934, Otoconcha, and Chilean Radiodiscus sp., but all with very little support. For clarity, we refer below only to BI posterior probability (PP) values, while the ML support values can be seen in Fig. 1.

The resulting tree shows that Punctoidea is not monophyletic (Fig. 1), a possibility that had already been alluded to by some previous authors (e.g., Wade et al. 2001, 2006; Holyoak et al. 2011; Nordsieck 2014). Rather, it is widely polyphyletic (see also the more comprehensive polyphyletism test in the Suppl. material 1: Part II), consisting of three distinct and well-supported groups within suborder Helicina: (1) a group containing Discidae and Oreohelicidae (1.0 PP), which we refer to a new superfamily Discoidea, based on the earliest available family-group name; (2) the Helicodiscidae, which forms a separate strongly supported group (1.0 PP) of uncertain affinity within suborder Helicina, in Stylommatophora; and (3) the Punctoidea sensu stricto, containing Endodontidae, Cystopeltidae, Punctidae and paraphyletic Charopidae (1.0 PP). Because the fossil record of Punctoidea sensu stricto is poorly understood (see Discussion below), and some of the internal branches of our phylogeny were not strongly supported, we have not attempted to estimate divergence times based on the molecular data.

Figure 1. 

Bayesian tree for the “Punctoidea”, rooted by the Hygrophila. Numbers shown on nodes are BI posterior probabilities (0 to 1) followed by ML bootstrap values (0 to 100%). Scale bar is substitutions per site.

This superfamily is strongly supported (Fig. 1) and is overall very well resolved, with all internal branches equally well supported. It contains two distinct groups, the families Oreohelicidae and Discidae. Our analysis of wider relationships within Stylommatophora (see Suppl. material 1: Part II) placed Discoidea close to infraorder Helicoidei, with strong support in the BI tree but weak support in the ML tree.

Oreohelicidae: This family, which is endemic to North America, is a strongly supported (1.0 PP) monophyletic group that is separate from Discidae and basal within Discoidea.

Discidae: This is a well-supported (1.0 PP) monophyletic group, which includes Anguispira Morse, 1864 and Discus Fitzinger, 1833. Our analysis indicates that the former genus is monophyletic, but the latter, as currently interpreted, is paraphyletic. This is not unexpected as Discus has been used a wastebasket taxon for North American and European discoid species, both Recent and fossil. However, what was surprising is that whereas two European species of Discus formed a separate basal clade (1.0 PP), a third European species, which was identified as D. ruderatus (Hartmann, 1821), the type species of the genus, grouped with North American species (1.0 PP). Further work is required to resolve the genus-level taxonomy of the species presently assigned to Discus, as well as the phylogenetic relationships of putative discid taxa from the Canary Islands (Holyoak et al. 2011; Cameron et al. 2013).

Our analysis indicated that samples identified as Anguispira alternata (Say, 1817) from the USA and Canada were very similar genetically and probably conspecific with one another. In contrast, the samples identified as A. kochi (Pfeiffer, 1846) from the USA and Canada differed markedly from one another, indicating that this taxon, which has a complex synonymy (MolluscaBase 2020), and is currently recognized as having a strongly disjunct distribution in North America, is probably a species complex.

Discoidea incertae sedis: The monotypic North American genus Radiodomus H.B. Baker, 1930 has previously been classified in subfamily Rotadiscinae of Charopidae, although Pilsbry (1948b) noted that the type species, Radiodomus abietum Baker, 1930, differed anatomically from other rotadiscines. Our phylogenetic analysis indicates that Radiodomus belongs instead in Discoidea, but further work is required to determine if it should be treated as the basal taxon in Discidae, or assigned to a separate, new family-level group within Discoidea.

This family is native to Central and North America (Zilch 1959). A species of helicodiscid that has been described from southeastern Brazil (Simone 2006) is actually an adventive North American species (Silva et al. 2020). Stenopylis coarctata (Möllendorff, 1894), which is apparently native to Malesia and northern Australia, has also been assigned to Helicodiscidae (e.g., Solem 1984; Stanisic et al. 2010), but this family-level classification requires reevaluation.

In our phylogeny Helicodiscidae is represented by two North American species of Helicodiscus Morse, 1864 that form a strongly supported (1.0 PP) clade. Although previously included in Punctoidea, our analysis suggests that Helicodiscidae does not belong in either Discoidea or the redefined Punctoidea. Its phylogenetic relationships with other taxa have not been precisely determined (see Suppl. material 1), but both our ML and BI trees position it (albeit with low support) close to Arionoidea and the ‘limacoid clade’ (now infraorder Limacoidei; Bouchet et al., 2017). As such the family is treated here as incertae sedis within suborder Helicina (in Stylommatophora), pending further work. Oopeltidae has also been previously classified in Punctoidea (Bouchet et al. 2017), although shown to be more closely related to Arionoidea (Sirgel 2012); whether or not Oopeltidae is closely related to Helicodiscidae requires investigation.

The Punctoidea, as redefined here, is a strongly supported clade (1.0 PP) clade containing representatives of Endodontidae, Cystopeltidae, Punctidae and Charopidae (Fig. 1). We could not reliably determine its position within Stylommatophora: our ML tree placed it as the basal group within suborder Helicina, while our BI placed it in a more derived position within Helicina (see Suppl. material 1: Part II).

Endodontidae: In our analysis, this family is represented by one species only, in the Polynesian genus Libera Garrett, 1881, but its split from the other punctoids is clear and strongly supported (1.0 PP). As such, Endodontidae is basal in the redefined Punctoidea, and is the sister taxon of the clade formed by the other punctoid families, as redefined below.

Cystopeltidae: Previously this family was interpreted as containing a single genus of semi-slugs, Cystopelta Tate, 1881, endemic to southeastern Australia, but our analysis indicated strong support (1.0 PP) for a monophyletic family-level group comprising two strongly supported clades (both 1.0 PP): one containing Cystopelta bicolor Petterd & Hedley, 1909, and two Tasmanian land snail taxa that were previously assigned to Charopidae, Diemenoropa kingstonensis (Legrand, 1871) and Scelidoropa officeri (Legrand, 1871); and the other containing South American land snail species in the genera Lilloiconcha Weyrauch, 1965 and Zilchogyra Weyrauch, 1965, which were previously assigned to Charopidae as well. These two clades possibly warrant separate subfamily-group status, but further work is required to test this. Our results indicate that the genus- and species-level classification of Lilloiconcha and Zilchogyra is in need of revision, as already alluded to by previous authors (e.g., Salvador et al. 2018b; Salvador 2019).

The charopid taxa that grouped in Cystopeltidae in our analysis have very similar shell morphology to some charopid taxa in the Punctidae + Charopidae clade (below). For the South American cystopeltid branch at least, a smooth protoconch might be a diagnostic character (Schileyko 2001). However, for many charopid genus groups it may not be possible to assign taxa to either family on the basis of shell characters alone. Further work is required to determine the family-level placement of the numerous extant taxa that are currently assigned to Charopidae but which were not included in our analysis, as well as to determine reliable family-level diagnostic characters.

The phylogenetic relationships of Cystopeltidae in our analysis appear to differ from the findings of Teasdale (2017), which indicated that Cystopelta purpurea Davies, 1912 (Cystopeltidae), and a putative representative of Punctidae that was identified as Paralaoma sp. (misspelled as Paraloama in the original), were sister species, separate from a group of two charopid species from Australia and South Africa, respectively. The reasons for this difference are unclear. It may be an artefact of the small number of punctoid samples and restricted geographic range in Teasdale’s (2017) analysis compared with our study.

Punctidae + Charopidae clade: Our analysis indicates strong support (1.0 PP) for a clade incorporating taxa that were previously assigned to Punctidae and Charopidae (excluding those that grouped with Cystopeltidae, see above). The phylogenetic relationships determined here suggest that whereas Punctidae, as previously interpreted, is monophyletic, Charopidae sensu Solem (1983: 47) and later authors is paraphyletic. At present there is insufficient information to determine whether Charopidae Hutton, 1884 would be best treated as a junior synonym of Punctidae Morse, 1864, or split into a series of separate monophyletic family units. In the meantime, for taxonomic stability, we suggest that Charopidae should be retained as a separate, paraphyletic family-level group, pending further work to determine the phylogenetic relationships of its constituent taxa (below).

The family-group name Punctidae is used here for a well-supported clade (1.0 PP), within which there is a strongly supported (1.0 PP) basal group containing the endemic New Zealand taxa Laoma Gray, 1850 and Phrixgnathus Hutton, 1882, corresponding to Laominae Suter, 1913, and a weakly supported group (0.56 PP) containing Paralaoma, which is native to Australasia but has a wide adventive distribution, and type genus Punctum Morse, 1864. As presently interpreted the latter genus has a predominantly Holarctic distribution in North America, Japan and extratropical Eurasia, but with records also from Central America, Hawai’i and tropical Africa (Pilsbry 1948b; Cowie et al. 1995; Wronski and Hausdorf 2010; de Winter 2017; Horsák and Meng 2018). Punctidae probably also includes other New Zealand punctid taxa listed by Spencer et al. (2009) and Australian punctid taxa listed by previous authors (e.g., Smith 1992; Schileyko 2002; Stanisic et al. 2010, 2018).

The family-group name Charopidae is provisionally retained here for charopid taxa other than those reassigned to Cystopeltidae (above). It includes taxa previously assigned to Charopinae Hutton, 1884 (in part), Phenacohelicidae Suter, 1892, Otoconchinae Cockerell, 1893, Flammulinidae Crosse, 1895, Patulastridae Steenburg, 1925, Rotadiscinae, Trachycystidae Schileyko, 1986, Ranfurlyinae Schileyko, 2001, and Therasiinae Schileyko, 2001. This diverse group of taxa has a very wide distribution that includes South America, South Africa, Australia, New Zealand and Oceania. The relationships within this group are as yet poorly resolved (see below), but our analysis indicates that it contains at least one strongly-supported group (1.0 PP), corresponding to Charopinae sensu stricto, which includes the type genus Charopa Albers & Martens, 1860, some other New Zealand taxa, and Sinployea Solem, 1983 from Oceania. Two of the constituent taxa, Flammulina E. von Martens, 1873 and Ranfurlya Suter, 1903, are the type genera of Flammulinidae and Ranfurlyinae, respectively, confirming that the latter two taxa are synonyms of Charopinae. Conversely, our analysis indicates that Charopinae does not include some genus-groups such Mocella Iredale, 1915, Stenacapha Smith & Kershaw, 1985 and Suteria Pilsbry, 1892, that were assigned to it by previous workers (e.g., Schileyko 2001).

Many of the charopid taxa in our analysis could not be reliably assigned to subfamily groups. The basal-most charopid taxon in our phylogeny is the African genus Chalcocystis Watson, 1934. It has been referred to the subfamily Trachycystinae (e.g., Schileyko 2001), but other authors have treated this subfamily as a synonym of Charopinae (e.g., Bouchet et al. 2017). This branch is strongly separated from the remaining punctoids, which suggests that Trachycystinae may have some biological reality if restricted to African taxa. Analysis of a larger sample of African taxa, including the type genus of the subfamily, is required to reliably determine the systematic relationships of this group.

The genus of semi-slugs Otoconcha forms a separate lineage in our analysis, albeit with poor support (0.55 PP). Otoconcha and Maoriconcha Dell, 1952 have been assigned to the endemic New Zealand subfamily Otoconchinae (e.g., Schileyko 2001), but further work is required to determine the phylogenetic relationships of these genera and the taxonomic status of Otoconchinae.

The New Zealand charopid taxon Suteria Pilsbry, 1892 also forms a separate lineage with poor support (0.6 PP) in our analysis. It was previously included in Charopinae (e.g., Schileyko 2001). Four other New Zealand “charopid” taxa, Neophenacohelix Cumber, 1961, Phenacohelix Suter, 1892, Phacussa Hutton, 1883 and Therasia Hutton, 1883, formed a poorly supported group (0.65 PP). The two first-named and two last-named taxa were previously assigned to Phenacohelicinae and Therasiinae, respectively. In our Bayesian tree, the New Zealand taxon Allodiscus Pilsbry, 1892, previously assigned to Phenacohelicinae (e.g., Schileyko 2001), grouped with these four taxa albeit with poor support (0.69 PP); in the ML tree, however, it was the sister taxon to Punctidae, again with poor support (50).

Stenacapha Smith & Kershaw, 1985 from Australia and Mocella Iredale, 1915 from New Zealand, both formerly included in Charopinae, formed a separate group in our analysis, albeit with moderate support only (0.93 PP).

Three of the South American taxa that were included in our analysis belong in two separate groups within the Punctidae + Charopidae clade. Radioconus amoenus (Thiele, 1927) and the Brazilian Radiodiscus sp. form a strongly supported group (1.0 PP), but the Chilean Radiodiscus sp. belongs to a separate lineage. Radiodiscus, as previously interpreted, is evidently polyphyletic; this is not unexpected, as the genus has historically functioned as a wastebasket taxon for South American charopids. Whether one or both these groups should have subfamily status, and whether or not either of them corresponds to Rotadiscinae, has not been determined. In any event, it is clear that New Zealand taxa that were assigned to Rotadiscinae by Climo (1989) and subsequent workers, including the genera Alsolemia Climo, 1981 and Mitodon Climo, 1989, belong instead in Charopinae (Fig. 1).

Several family-level taxa that have previously been treated as synonyms of Charopidae, or subfamily-groups within Charopidae, were not included in the analysis. These include (in chronological order): Amphidoxinae Thiele, 1931 (Chile); Dipnelicidae Iredale, 1937 (Australia); Hedleyoconchidae Iredale, 1942 (Australia); Pseudocharopidae Iredale, 1944 (Lord Howe Island); Semperdoninae Solem, 1976 (Micronesia); Trukcharopinae Solem, 1983 (Micronesia); and Flammoconchinae Schileyko, 2001 (New Zealand). Thysanotinae Godwin-Austen, 1907 (southern Asia and Pacific islands) has been included in Charopidae by some authors (e.g., Bouchet et al., 2017), but ongoing studies suggest that it does not belong in Punctoidea (Fred Naggs, pers. comm.).

The poor resolution in our analysis of some phylogenetic relationships within Charopidae may have been because of insufficient sequence information or inadequate sampling of taxa. The latter is more likely, given that the sequence data were sufficient to resolve phyletic relationships with strong support within the other families that were examined. Although the analysis included samples of 24 genus-level charopid taxa (Table 1), this represents only a very small proportion of the overall diversity of this paraphyletic group. For instance, the Australian fauna includes 104 named genus groups of charopids (Stanisic et al. 2010, 2018), of which we sampled three taxa (c 3%) only. In the New Zealand fauna, there are 45 named charopid genera (Spencer et al. 2009), 14 of which (31%) were included in our analysis. The fauna of Oceania includes 20 named charopid genera (Solem 1983), of which we sampled one taxon (5%) only. For large, diverse and reasonably old groups, it is deemed that adding taxa usually outweighs adding sequence data (Pollock et al. 2002; Zwickl and Hillis 2002; Heath et al. 2008; Nabhan and Sarkar 2011). Obtaining a better resolution of the subfamily-level groups within the clade of Punctidae + Charopidae will require a broader coverage of species, both taxonomically and geographically.

This superfamily has a Laurasian distribution. Based on our present phylogeny of extant species, Oreohelicidae and Radiodomus are North American, and the most basal Discidae are European, while a group of more derived discids includes both European and North American taxa. The phylogenetic relationships of purported Discidae from the Canary Islands are as yet undetermined.

Records of land snails from the Carboniferous of North America that were attributed to Discidae and other stylommatophoran groups by Solem and Yochelson (1979) are now considered to be non-stylommatophoran eupulmonates (e.g., Bandel 1991, 1997; Mordan and Wade 2008). The oldest known fossil taxa assigned to Discoidea are from the Late Cretaceous of Alberta, Canada. They include Discus sandersonae (Russell, 1929), in family Discidae (Pilsbry, 1939), and Oreohelix obtusata (Whiteaves, 1885), Radiocentrum anguliferum (Whiteaves, 1885) and R. thurstoni (Russell, 1926), all in family Oreohelicidae, (Henderson 1935; Tozer 1956; Roth 1986). Other fossil species of Radiocentrum Pilsbry, 1905 are known from the Paleocene of Alberta, Eocene of Wyoming, and Oligocene of Colorado, whereas the Quaternary distribution of this genus group is restricted to southwestern USA and northwestern Mexico (Roth 1986; Hochberg et al. 1987). Fossil species of Oreohelix Pilsbry, 1904 are known from Late Cretaceous, Paleocene and Eocene faunas from Alberta to Utah (Roth 1986). Oreohelix is the most diverse genus group in the extant North American land snail fauna, with 79 species recorded from western Canada, USA and Mexico (Pilsbry 1948a, 1948b; Nekola 2014).

In North America relatively few fossil species of Discus sensu lato are known from the Cenozoic, with records from the Late Paleocene/Early Eocene of Utah, Eocene of Wyoming and Montana, and Miocene of Oregon (Pilsbry 1939; La Roque 1960; Pierce and Constenius 2014). In Europe the oldest known fossil taxon in Discidae is Discus perelegans (Deshayes, 1863) from the Late Paleocene/Early Eocene of the Paris Basin, France (Wenz 1923). Discus sensu lato evidently underwent an extensive radiation in the mid Paleogene of Europe, with several species represented in fossil faunas of Eocene age from southern England and the Paris Basin (Preece 1982; Pacaud and Le Renard 1995). The Neogene land snail fauna of Europe also contains numerous fossil species that have been assigned to this paraphyletic genus group (e.g., Harzhauser et al. 2014; Höltke et al. 2016, 2018).

Anguispira has a fossil and extant distribution restricted to North America. The oldest known fossil is Anguispira cf. alternata (Say, 1816) from the Eocene of Montana, USA (Pierce and Constenius 2014), indicating that the split between this genus and Discus sensu lato took place in the Eocene or earlier. The Discidae presumably diverged from the Oreohelicidae and Radiodomus lineages in the Late Cretaceous or earlier.

Fossils of helicodiscid taxa are known from the Early Miocene of Europe (genus Lucilla Lowe, 1852; Nordsieck 2014; Salvador 2014) and the Late Miocene of North America (Liggert 1997; Gladstone et al. 2019), indicating a former wider Laurasian distribution.

This superfamily is distributed almost worldwide, but given that the greatest diversity of extant taxa is in the Southern Hemisphere, with one genus only in the Northern Hemisphere, it is likely of Gondwanan origin. Interpretation of the biogeographic history of the Punctoidea is hindered by a relatively sparse fossil record, and the difficulty in reliably assigning fossil material, which in many cases is poorly preserved, to family-level groups on the basis of shell morphology alone. Our finding that some extant taxa that were previously assigned to Charopidae actually belong in Cystopeltidae has further complicated matters, because, as noted above, shell characters of charopid genus groups do not appear to be a reliable indicator of family-level phylogenetic relationships. Despite these limitations, some useful biogeographic information can be gleaned from the fossil record.

The oldest known fossil taxon that could possibly be assigned to Punctoidea is Radiodiscus santacrucensis Morton, 1999, from the Lower Cretaceous of Argentina (Morton 1999; Rodríguez et al. 2012), although the genus-level placement of this species is probably incorrect and requires re-evaluation (Salvador et al. 2018a), and the family-level placement is unclear. All other known fossils of Punctoidea are from the Cenozoic.

The oldest fossil species that can be reliably assigned to Endodontidae is Cookeconcha subpacificus (Ladd, 1958) from the Lower Miocene of Bikini Atoll, Marshall Islands (Ladd 1958). It is most closely related to Pleistocene and Recent congeners from Midway Atoll and Hawai’i, respectively (Solem 1976, 1977, 1983). The monotypic fossil taxon Hebeispira hebeiensis Youluo, 1978, of “Early Tertiary” age from the Bohai coastal plain in North China, was assigned to Endodontidae. However, examination of images of type material (Youluo 1978: pl. 30, figs 12–14) indicates that it belongs in neither Endodontidae nor Punctoidea and is likely a freshwater Planorbidae. Likewise, records of undetermined Endodontidae from the Early/Middle Miocene of Germany by Moser et al. (2009) have been refuted (Nordsieck 2014; Salvador and Rasser 2014).

The Endodontidae are otherwise known from Oceania only, on volcanic and uplifted islands between Tuvalu, Pitcairn Islands and Hawai’i, with an outlying genus-group in Palau, Micronesia (e.g., Solem 1976, 1983; Abdou and Bouchet 2000; Brook 2010; Sartori et al. 2014). No endodontids are known from the Holocene faunas of Marshall Islands and Midway Atoll. Taxa that were present there during mid to late Cenozoic time when these islands were high-standing presumably became extinct when the islands subsided and became atolls (Solem 1976). Similar histories of endodontid species colonizing oceanic islands by over-water dispersion, undergoing radiations at species and sometimes also genus level, and becoming extinct when host islands subsided to, and below, sea level, probably played out across much of Oceania during the Neogene and Quaternary, and probably also earlier in the Paleogene (see below).

Thirteen species of Cenozoic fossil land snails from South America have been included in Punctoidea with varying degrees of confidence (Miquel and Bellosi 2007; Rodriquez et al. 2012; Miquel and Rodríguez 2015; Salvador et al. 2018a). This includes species in extant genus groups that we have assigned to Cystopeltidae (i.e., Lilloiconcha, Zilchogyra) and the Punctidae + Charopidae clade (i.e., Punctum, Radiodiscus), along with other extant and extinct genus groups whose family-level placement has not been determined. The earliest fossil records of Lilloiconcha, Radiodiscus and Zilchogyra are from the Eocene of Argentina (Miquel and Bellosi 2007; Rodriquez et al. 2012), and the earliest (and only) record of Punctum from South America is from the Early/Middle Miocene of Argentina (Miquel and Rodríguez 2015; Salvador et al. 2018a). Even with uncertainties, this indicates that Cystopeltidae, Punctidae and ‘Charopidae’ existed in South America as separate lineages by Eocene time.

In New Zealand, where extant Punctoidea are extremely diverse at both genus and species level, the pre-Quaternary fossil record is unfortunately very limited. The oldest known fossils are seven species of Early Miocene age from Otago (Marshall and Worthy 2017). All but one of these species have been assigned to extant genera, with one in Punctidae (i.e., Paralaoma), two in genera that our analysis indicated belong in Charopinae (i.e., Charopa, Fectola Iredale, 1915), and one other charopid genus (Neophenacohelix). The extinct genus Atactolaoma Marshall & Worthy, 2017 probably belongs in Punctidae, but the family and subfamily status of the charopid taxa Cavellia Iredale, 1915 and Dendropa Marshall & Worthy, 2017 has not been determined. As yet, we do not know if Cystopeltidae are and/or were ever present in the New Zealand region.

In Oceania, the only known pre-Quaternary fossil charopid is Vatusila eniwetokensis (Ladd, 1958) from the Late Miocene of Eniwetok Atoll, Marshall Islands (Solem 1976, 1983). This genus, which is genetically closely related to Sinployea (M. Kennedy, unpublished data) and probably belongs in Charopinae, has a Holocene distribution extending from Tuvalu south to Tonga and Niue (Solem, 1983). As with Endodontidae on Marshall Islands and Midway Atoll (see above), the distribution of Vatusila within Oceania evidently changed markedly during the Neogene, in response to patterns of over-water dispersion and the emergence and foundering of oceanic islands.

In Europe and North America, the Punctoidea is represented by one genus only, as noted above. The oldest putative fossil Punctum in Europe is P. oligocaenicum Zinndorf, 1901 of Late Oligocene age from Germany (Wenz, 1923). However, Harzhauser et al. (2014) noted that this species may not belong to Punctum, and the family placement therefore also requires re-evaluation. Fossil species that undoubtedly belong in Punctum are well represented in Neogene strata in continental Europe (Harzhauser et al. 2014; Höltke et al. 2016). In North America the oldest putative fossil Punctum, and the only pre-Quaternary record of this genus, is P. alveus Pierce, 1992, from the Late Oligocene/ Early Miocene of Montana, USA (Pierce 1992).

Australia, like New Zealand, has a diverse extant punctoid fauna, but whereas the New Zealand fauna is dominated at the species level by Punctidae, the Australian fauna is dominated by charopid taxa. Our analysis showed that the Tasmanian charopid fauna includes representatives of Cystopeltidae and the Punctidae + Charopidae clade, but the family-group affinities of the vast majority of Australian taxa have not yet been determined, and the paleobiogeographic history of the Australian punctoid fauna is not known. Similarly, the family-group affinities and paleobiogeographic histories of charopid taxa from Africa, New Caledonia and Saint Helena, are not known.

In summary, some extant punctoid genera are interpreted as having stratigraphic ranges extending back to the lower Neogene or middle Paleogene, and fossil assemblages from South America, New Zealand and Oceania also include extinct punctoid genera (e.g., Solem 1977; Miquel and Rodríguez 2015; Marshall and Worthy 2017). The fossil record in South America indicates that Cystopeltidae, Punctidae in the restricted sense and ‘Charopidae’ existed as separate family-level groups by Eocene time, and thus must have diverged sometime prior to that. The oldest known fossils of Endodontidae are Early Miocene in age, but the basal position of this family in Punctoidea suggests that it diverged from the lineages giving rise to Cystopeltidae and the Punctidae + Charopidae clade in the Paleocene or earlier. The oldest known fossils assigned to Punctidae and Charopinae are of Late Oligocene and Early Miocene age, respectively (Wenz 1923; Pierce 1992; Marshall and Worthy 2017), indicating that these groups had diverged by the Late Paleogene. By Early Miocene time the Punctidae had attained a very wide distribution, with at least two genus groups in New Zealand (Atactolaoma, Paralaoma), and species of Punctum in South America, North America and Europe, but the latter genus (and Punctidae in general) evidently subsequently became extinct in South America. The basal group of Punctidae in our phylogenetic analysis contains the New Zealand genera Laoma and Phrixgnathus. These two genera are not known from any pre-Quaternary fossil assemblages in New Zealand or elsewhere, but must have diverged from the group of Paralaoma and Punctum in the Oligocene or earlier. The shells of Laoma and Phrixgnathus typically have a color pattern of radial stripes and zigzags, whereas shells of Paralaoma and Punctum are generally smaller and uniformly brown in color. Whether the Laoma-Phrixgnathus lineage originated in the New Zealand region in the Paleogene, or dispersed there from elsewhere later in the Cenozoic, is not known.

From a morphological and evolutionary perspective it is interesting to note that, although the vast majority of punctoid taxa have coiled external shells that animals can fully retract into, shell reduction leading to limacization has occurred independently in the endemic Australian genus Cystopelta (Cystopeltidae), and in separate lineages within the Punctidae + Charopidae clade, including the endemic New Zealand genera Ranfurlya (Charopinae) and Otoconcha (Otoconchinae). The phylogenetic relationships of Flammoconcha Dell, 1952, another endemic New Zealand genus of punctoid semi-slugs, have not yet been determined. There are, however, no known cases of limacization within Endodontidae, which might have been precluded by aspects of their pallial anatomy (Solem, 1976).