Phylogenetic analyses with four new Cretaceous bristletails reveal inter-relationships of Archaeognatha and Gondwana origin of Meinertellidae

Abstract

Based on fifteen Archaeognatha (=Microcoryphia) specimens from Myanmar (Burmese) amber, including males, females and immatures, two new genera and four species, Cretaceomachilis longa sp.n., Unimeinertellus abundus gen. et sp.n., U. bellus sp.n. and Nullmeinertellus wenxuani gen. et sp.n., are described. Phylogenetic analyses of taxa in Archaeognatha were conducted using Maximum parsimony and Bayesian inference based on morphological characters and DNA sequence data. Our results confirm the phylogenetic position of the new genera, clarify the monophyly of Meinertellidae and indicate that the ‘paleo-types’ excluding Ditrigoniophthalmus are nested within the Machilidae group, but suggest that the three subfamilies within Machilidae may be artificial. The diversity of meinertellids with derived characters found from the Cretaceous indicate that the divergence time of Machilidae and Meinertellidae is much earlier than the Cretaceous. We propose the possibility that Meinertellidae might have originated on Gondwana.

Full text

Phylogenetic analyses with four new Cretaceous bristletails reveal
inter-relationships of Archaeognatha and Gondwana origin of
Meinertellidae
Weiting Zhang
a
,HuLi
b,
*, Chungkun Shih
c,d
, Aibing Zhang
c
and Dong Ren
c,
*
a
Geoscience Museum, Hebei GEO University, 136 huaiandonglu, Shijiazhuang, Hebei 050031, China;
b
Department of Entomology, China
Agricultural University, 2 Yuanmingyuan West Road, Beijing 100193, China;
c
College of Life Sciences, Capital Normal University, 105
Xisanhuanbeilu, Haidian District, Beijing 100048, China;
d
Department of Paleobiology, Smithsonian Institution, National Museum of Natural
History, Washington, DC 20013, USA
Accepted 2 June 2017
Abstract
Based on fifteen Archaeognatha (=Microcoryphia) specimens from Myanmar (Burmese) amber, including males, females and
immatures, two new genera and four species, Cretaceomachilis longa sp.n., Unimeinertellus abundus gen. et sp.n.,U. bellus sp.n.
and Nullmeinertellus wenxuani gen. et sp.n., are described. Phylogenetic analyses of taxa in Archaeognatha were conducted using
Maximum parsimony and Bayesian inference based on morphological characters and DNA sequence data. Our results confirm
the phylogenetic position of the new genera, clarify the monophyly of Meinertellidae and indicate that the ‘paleo-types’ exclud-
ing Ditrigoniophthalmus are nested within the Machilidae group, but suggest that the three subfamilies within Machilidae may
be artificial. The diversity of meinertellids with derived characters found from the Cretaceous indicate that the divergence time
of Machilidae and Meinertellidae is much earlier than the Cretaceous. We propose the possibility that Meinertellidae might have
originated on Gondwana.
©The Willi Hennig Society 2017.
Introduction
Archaeognatha, commonly called jumping bristletails,
are the sister group of all other insects. This order of
wingless insects comprises approximately 500 extant
species (Sturm and Machida, 2001). Defining features of
the Archaeognatha are the large and contiguous com-
pound eyes, three ocelli, monocondylar mandibles,
seven-segmented maxillary palps, the legs bearing coxal
stylets, abdomen segments bearing stylets and eversible
vesicles, one long central caudal filament, and two short
lateral cerci (Sturm and Bach de Roca, 1993; Sturm and
Machida, 2001). Bristletails are usually active noctur-
nally, feeding on litter, detritus, algae, lichens and
mosses, sheltering beneath bark or in leaf litter during
the day (Gullan and Cranston, 2005).
A review of taxonomy of Archaeognatha
Archaeognatha encompasses two suborders: Monura
and Machilida (Bechly and Stockar, 2011). Monura
was previously erected as an order for accommodating
the Palaeozoic family Dasyleptidae (Sharov, 1957), but
it was down-ranked later to a suborder of Archaeog-
natha (Bitsch and Nel, 1999). Bechly and Stockar
(2011) reconfirmed Monura as a suborder of
Archaeognatha, and proposed another suborder,
Machilida, including Ditrigoniophthalmus and super-
family Machiloidea that comprises two extant families:
Machilidae and Meinertellidae.
The genera Ditrigoniophthalmus,Charimachilis and
Mesomachilis were accommodated in Machilidae sensu
*Corresponding authors.
E-mail addresses: rendong@mail.cnu.edu.cn and tigerleecau@
hotmail.com
Cladistics
Cladistics (2017) 1–23
10.1111/cla.12212
©The Willi Hennig Society 2017

Remington (1954) originally, but were then removed
from Machilidae and treated as Machiloidea incertae
sedis (Sturm and Bach de Roca, 1993). Due to their
unique characters, they were considered to evolved
independently from the ancestral group of Machilidae
(restr.) and Meinertellidae (Sturm and Bach de Roca,
1993). Compared with other machiloids, these genera
bear relatively primitive structures and thus, Sturm and
Bach de Roca (1993) used ‘palaeoform(s)’ to denote
them. However, this term has been used predominantly
for geomorphological structures in both sedimentary
and stratigraphic studies. To avoid confusion with geo-
logical terms, we replace ‘palaeoform(s)’ with ‘paleo-
type(s)’. Turquimachilis, established recently, was also
considered as ‘paleo-type’ and placed into the incertae
sedis group together with Charimachilis (Bach de Roca
et al., 2013).
Triassomachilidae was erected within Archaeognatha
for a Triassic species, Triassomachilis uralensis (Sharov,
1948). But this species was considered to be an Ephe-
meroptera nymph by Bitsch and Nel (1999), and Sinit-
shenkova (2000) then synonymized the Triassomachilis
with the fossil mayfly genus Mesoneta, which has been
widely accepted to date (Rasnitsyn, 2002; Bechly and
Stockar, 2011; Mendes and Wunderlich, 2013).
A review of published data on Archaeognatha phylogeny
Phylogenetic relationships within Archaeognatha
have been discussed in several studies (Bitsch and Nel,
1999; Sturm and Machida, 2001; Koch, 2003). Bechly
and Stockar (2011) proposed that Monura represent the
sister group of all recent bristletails. Sturm and Bach de
Roca (1993) considered Machilidae sensu Remington to
be a paraphyletic group, and they removed Ditrigonio-
phthalmus,Charimachilis and Mesomachilis from
Machilidae. But Koch (2003) proposed the possibility
that ‘paleo-types’ (except Ditrigoniophthalmus) and
remaining Machilidae form a paraphyletic assemblage
with respect to Meinertellidae. In the most recent phylo-
genetic result based on molecular data, the monophyly
of Machilidae was also challenged, and the relation-
ships among archaeognathan subfamilies, seemed to be
tangled (Ma et al., 2015). Consequently, the phyloge-
netic positions of the ‘paleo-types’, and the monophyly
of Machilidae and their subfamilies, are still unclear
and controversial. Herein we present a phylogeny of
Archaeognatha based on morphological characters and
molecular data. Fossil representatives are included in
our phylogenetic analyses to shed new light on the rela-
tionships and evolution of taxa in Archaeognatha.
A review of published data on Archaeognatha fossils
Archaeognatha are the sister group of other living
insects (Grimaldi and Engel, 2005). Fossil species of
Archaeognatha are known from the Devonian to
recent (Table 1). Some fragments found from Devo-
nian are supposed to be the oldest Archaeognatha fos-
sil records (Shear et al., 1984; Labandeira et al., 1988).
The oldest undoubted fossil species, Dasyleptus lucasi
Brongniart, 1885; Dasyleptus noli Rasnitsyn, 1999 and
Dasyleptus rowlandi Rasnitsyn (in Rasnitsyn et al.,
2004), came from the Late Carboniferous (Kasimo-
vian–Gzhelian). Up to now, all of the Palaeozoic spe-
cies are placed in Dasyleptidae. Sturm and Poinar
(1998) reported the earliest Mesozoic fossils, Cretaceo-
machilis libanensis from Lebanese amber. Grimaldi
et al. (2002) mentioned one Machilidae and five
unidentified Archaeognatha from Myanmar amber,
and one more specimen that probably belongs to
Macropsontus was described recently (Mendes and
Wunderlich, 2013). A number of fossil species were
reported from Baltic amber (Koch and Berendt, 1854;
Handlirsch, 1907; von Olfers, 1907), but many of them
are junior synonyms, which were summarized by
Silvestri (1912). Two Neomachilellus fossil species,
N. dominicanus Sturm and Poinar, 1997 and N. ezetae-
lenensis Riquelme and Montejo in Riquelme et al.,
2015 occur in Miocene amber from Mexico and the
Dominican Republic. Besides body fossils, eleven
archaeognathan ichnofossils were reported from the
late Carboniferous to the Early Permian (Table 1),
and these ichnofossils were found mainly in the USA
(Lucas et al., 2005a,b; Getty et al., 2013; Mendes and
Wunderlich, 2013).
Recently, we collected 15 archaeognaths in Myan-
mar amber, which are an important supplement to
Archaeognatha records and provide new evidence for
their phylogeny and evolution. Although the age of
Myanmar amber has been previously controversial
(Zherikhin and Ross, 2000; Grimaldi et al., 2002;
Ross, 2010), a recent radioisotopic date has been
established at 98.79 0.62 Ma (Cruickshank and Ko,
2003; Shi et al., 2012), equivalent to the earliest Ceno-
manian and approximately 1 Myr within the boundary
between the Early and Late Cretaceous (Walker et al.,
2012).
Materials and methods
Materials and terminology
The new amber type specimens are housed at the
fossil insect collection of the Key Lab of Insect Evolu-
tion and Environmental Changes, at the College of
Life Sciences, Capital Normal University (CNUB,
Dong Ren, Curator), in Beijing, China. The amber
pieces were polished in order to optimize the viewing
and photography of specimens for taxonomic study.
They were examined with the Nikon SMZ25 dissecting
2Zhang et al. / Cladistics 0 (2017) 1–23

Table 1
Fossil records of Archaeognatha
Age Location Taphonomy Literature Mark
Dasyleptidae
? Archaeognatha D
1
Canada: Quebec Compression Labandeira et al., 1988; a
? Archaeognatha D
2
USA: New York Compression Shear et al., 1984; b
Dasyleptus lucasi C
2
France Compression Brongniart, 1885; c
Dasyleptus noli C
2
France Compression Rasnitsyn, 1999; c
Dasyleptus rowlandi P
1
USA: New Mexico Compression Rasnitsyn et al., 2004; d
Dasyleptus artinskianus P
1
USA: Kansas Compression Engel, 2009; e
Dasyleptus sharovi P
1
USA: Kansas Compression Durden, 1978; Bechly and
Stockar, 2011;
e
Dasyleptus brongniarti P
2
Russia: Kuznetsk Basin Compression Sharov, 1957; f
Dasyleptus triassicus T
2
Switzerland: Monte San
Giorgio
Compression Bechly and Stockar, 2011; g
Mitchellichnus cf.
ferrydenensis
C
2
USA: Massachusetts Trace fossil Getty et al., 2013; c
Stiallia pilosa C
2
USA: Kansas,
Massachusetts
Trace fossil Buatois et al., 1998; Getty et al.,
2013;
c
Stiaria elegans C
2
USA: Massachusetts Trace fossil Getty et al., 2013; c
Stiaria intermedia C
2
–P
1
USA: Kansas,
Massachusetts, New
Mexico
Trace fossil Buatois et al., 1998; Getty et al.,
2009, 2013;
c–e
Stiaria sp. P
1
USA: New Mexico Trace fossil Lucas et al., 2005a; e
Tonganoxichnus buildexensis C
2
USA: Kansas, Indiana,
Massachusetts
Trace fossil M
angano et al., 1997, 2001; Getty
et al., 2013;
c
Tonganoxichnus ottawensis C
2
USA: Kansas Trace fossil M
angano et al., 1997, 2001; c
Tonganoxichnus apacheensis P
1
USA: New Mexico Trace fossil Braddy and Briggs, 2002; Minter
and Braddy, 2009;
e
Tonganoxichnus robledoensis P
1
USA: New Mexico Trace fossil Braddy and Briggs, 2002; e
cf. T. robledoensis P
1
USA: New Mexico Trace fossil Lucas et al., 2005a; e
cf. T. robledoensis P
1
USA: New Mexico Trace fossil Lucas et al., 2005b; e
Machilidae
1 “Machilid” without details K
1
/K
2
Myanmar Amber Grimaldi et al., 2002; h
Machilis acuminata E
2
Baltic Amber Koch and Berendt, 1854; i
Machilis albomaculata E
2
Baltic Amber Menge, 1854; von Olfers, 1907; i
Machilis anguea E
2
Baltic Amber Koch and Berendt, 1854; i
Machilis boops E
2
Baltic Amber von Olfers, 1907; Silvestri, 1912; i
Machilis capito E
2
Baltic Amber von Olfers, 1907; Silvestri, 1912; i
Machilis confinis E
2
Baltic Amber Koch and Berendt, 1854; i
Machilis corusca E
2
Baltic Amber Koch and Berendt, 1854; Silvestri,
1912;
i
Machilis diastatica E
2
Baltic Amber von Olfers, 1907; Silvestri, 1912; i
Machilis electa E
2
Baltic Amber Koch and Berendt, 1854; i
Machilis imbricata E
2
Baltic Amber Koch and Berendt, 1854; i
Machilis longipalpa E
2
Baltic Amber Koch and Berendt, 1854; i
Machilis macrura E
2
Baltic Amber Menge, 1854; Handlirsch, 1907;
Silvestri, 1912;
i
Machilis palaemon E
2
Baltic Amber von Olfers, 1907; Silvestri, 1912; i
Machilis saliens E
2
Baltic Amber Menge, 1854; i
Machilis seticornis E
2
Baltic Amber Koch and Berendt, 1854; i
Machilis?caestifera E
2
Baltic Amber Silvestri, 1912; i
Praemachilis cineracea E
2
Baltic Amber von Olfers, 1907; Silvestri, 1912; i
?Petrobius sp. E
2
Baltic Amber H€
adicke et al., 2014; i
1 Machilinae species E
2
Baltic Amber H€
adicke et al., 2014; i
Meinertellidae
Cretaceomachilis libanensis K
1
Lebanon Amber Sturm and Poinar, 1998; j
cf. Macropsontus K
1
/K
2
Myanmar Amber Mendes and Wunderlich, 2013; k
Cretaceomachilis longa sp.n. K
1
/K
2
Myanmar Amber This paper k
Unimeinertellus abundus gen.
et sp.n.
K
1
/K
2
Myanmar Amber This paper k
Unimeinertellus bellus sp.n. K
1
/K
2
Myanmar Amber This paper k
Nullmeinertellus wenxuani gen.
et sp.n.
K
1
/K
2
Myanmar Amber this paper k
Non-identified K
2
USA: New Jersey Amber Sturm and Machida, 2001; l
Zhang et al. / Cladistics 0 (2017) 1–23 3

microscope. Photographs were acquired by a Nikon
DS-Ri2 Digital Camera system. Line drawings were
made with Photoshop CS graphic software. The body
length was measured along the midline from the ante-
rior margin of the head to the apex of the abdomen,
minus appendicular structures; all measurements are
given in mm. Terminology broadly follows Sturm and
Machida (2001). Ovipositor type is according to Sturm
and Bach de Roca (1993).
Phylogenetic methods
Sampling. The relationships of all taxa within
Archaeognatha, including both extant and fossil species,
have rarely been studied. Accordingly, we expand
previous treatments of the clade to include living and
fossil representatives of the principal groups within the
order. We sampled a total of 26 terminal species,
comprising 24 ingroups (18 extant species and 6 fossil
species) and two outgroups (Appendix S1). The
sampled ingroups represent the extinct family
Dasyleptidae and two extant families Machilidae and
Meinertellidae. Considering that the phylogenetic
position of ‘paleo-types’ is still contentious,
Ditrigoniophthalmus, Charimachilis, Mesomachilis and
Turquimachilis were included in our analyses. All extinct
genera (Dasyleptus, Cretaceomachilis, Unimeinertellus
gen.n. and Nullmeinertellus gen.n.) were also included,
but the genera established for trace fossils were
excluded. The fossil representatives were selected
according to the relative completeness of the specimens
and the resultant proportion of missing characters in
the morphological character matrix (Appendix S1).
Outgroups were selected based on the most recent
phylogenetic analyses of Hexapoda (Misof et al.,
2014). Archaeognatha are the most basal group in
Insecta. Due to Diplura and Collembola being the
closest extant relatives of bristletails, and their rela-
tively basal position within Hexapoda, two species—
Campodea ottei Allen, 2002 (Diplura) and Cryptopygus
antarcticus Willem, 1901 (Collembola)—were selected
as outgroups for maximum parsimony analysis based
on morphological data. Because of a lack of 18S and
28S rDNA sequences, the outgroup Campodea ottei
was not included in our Bayesian analysis based on
total evidence data.
Morphological data. The phylogenetic analysis was
performed using 34 morphological characters that
mainly refer to earlier studies (Sturm and Machida,
2001; Koch, 2003). These characters were identified
and coded as unordered and with equal weight.
Inapplicable and unknown characters were respectively
coded as “-” and “?”. Descriptions of character states
of morphological characters are given in Appendix 1.
The data matrix is given in Appendix S1.
Molecular data. Sequences of 12S, 16S, 18S and 28S
rRNA genes, cytochrome oxidase I (COI) and
cytochrome oxidase II (COII) were retrieved from
GenBank for eleven extant archaeognaths and one
outgroup Cryptopygus antarcticus (Appendix S2).
Protein-coding genes (COI and COII) were aligned
individually based on codon-based multiple alignments
using the Muscle algorithm implemented in MEGA
6.06 (Tamura et al., 2013). Sequences of rRNA genes
were aligned using the MAFFT 7.0 online server with
the G-INS-i strategy (Katoh and Standley, 2013).
Genes were concatenated and the final dataset includes
a total of 7758 aligned base pairs.
The optimal partition strategy and models of molec-
ular data were selected by PartitionFinder v.1.1.1
(Lanfear et al., 2012). We created an input configura-
tion file that contained 10 pre-defined partitions: four
partitions for four rRNA genes and six partitions for
codon positions of COI and COII. We use the
“greedy’’ algorithm with branch lengths estimated as
“unlinked” and used the Bayesian information crite-
rion (BIC) to search for the best-fit scheme. The data
were partitioned into three parts as follows: (i) 18S,
28S rRNA genes and first and second codon positions
of COI and COII with GTR+I+G model; (ii) the third
Table 1
(Continued)
Age Location Taphonomy Literature Mark
Neomachilellus sp. N
1
Mexico: Chiapas Amber Wygodzinsky, 1971; m
Neomachilellus
(Praenomachilellus)
dominicanus
N
1
Dominican Republic Amber Sturm and Poinar, 1997; m
Neomachilellus
(Praenomachilellus)
ezetaelenensis
N
1
Mexico: Chiapas Amber Riquelme et al., 2015; m
Meinertellus sp. Qh Colombia Copal Mendes, 1997 n
D
1
, Early Devonian; D
2
, Middle Devonian; C
2
, Late Carboniferous; P
1
, Early Permian; P
2
, Middle Permian; T
2
, Middle Triassic; J
1
, Early
Jurassic; J
2
, Middle Jurassic; J
3
, Late Jurassic; K
1
, Early Cretaceous; K
2
, Late Cretaceous; E
2
, Eocene; N
1
, Miocene; Qh, Recent.
4Zhang et al. / Cladistics 0 (2017) 1–23

codon positions of COI and COII with HKY+I+G
model; and (iii) 12S and 16S rRNA genes with
GTR+I+G model.
Maximum parsimony (MP) analysis. The character
matrix (Appendix S1) was edited using NDE v.0.5.0
(Page, 2001). Cladograms based on character
datasets were recovered using NONA (Goloboff,
1998) with the WinClada interface (Nixon, 2002).
Tree searches used the heuristic search method
(options set to hold 10 000 trees, 1000 replications,
100 starting tree replications, multiple TBR +TBR
search strategy). Bremer’s decay index was calculated
using TreeRot v.3 v.4.0 (Sorenson and Franzosa,
2007) and PAUP*v.4.0b10 (Swofford, 2002) to
assess tree robustness and relative support for
individual clades.
Bayesian inference (BI) analysis. Bayesian analysis
of a total-evidence dataset including 34 morphological
characters and sequences of six genes from 25 species
(24 archaeognaths and one outgroup) was performed
in MrBayes 3.2.3 (Ronquist and Huelsenbeck, 2003;
Ronquist et al., 2012). Four data partitions were used:
three partitions for molecular data with the best model
selected by the software PartitionFinder, and the
fourth partition for morphological data with the Mk
model (Lewis, 2001) and gamma distribution
(Appendix S3). Two separate runs, each having
unlinked partitions and four Bayesian Markov chain
Monte Carlo (MCMC) chains (three heated and one
cold) ran simultaneously for a total of 10 million
generations, with sampling every 1000 generations and
the first 25% discarded as burn-in. Stationarity was
considered to be reached when the average standard
deviation of split frequencies was below 0.01. A
majority-rule consensus tree was computed with
posterior probabilities (PP) for each node.
Biogeographical analysis
Two approaches were used for the ancestral charac-
ter state reconstruction of the geographic distribution
of Meinertellidae. First, we used parsimony ancestral
state reconstruction implemented in Mesquite (Mad-
dison and Maddison, 2014). Second, we used a disper-
sal-vicariance (DIVA) optimization model (Ronquist,
1997) implemented in the programme RASP2.0 Beta
(Yu et al., 2010) with default settings. The phyloge-
netic tree based on total-evidence obtained from Baye-
sian analysis was used for biogeographical analysis.
Eight biogeographical areas were recognized, namely:
A, Asia excluding Arabian Peninsula and Oriental
region; B, Arabian Peninsula; C, Oriental region; D,
Europe; E, Africa; F, Oceania; G, South America; H,
North America. Biogeographical distribution data for
Meinertellidae were compiled mainly from the litera-
ture (Sturm and Bach de Roca, 1993).
Results
Taxonomy
Order Archaeognatha
Family Meinertellidae Verhoeff, 1910
Genus Cretaceomachilis Sturm and Poinar, 1998
Type species.C. libanensis Sturm and Poinar, 1998
Revised diagnosis. Distal segment of labial palps
slightly broadened; both middle and hind legs with
coxal stylets; tarsi with three tarsomeres; in male, penis
probably shorter than half the length of abdominal
coxites IX; in female, ovipositor extending beyond the
ends of stylets IX.
Cretaceomachilis longa sp.n.
(Fig. 1)
Etymology. The species name is derived from the
Latin word “longa” (long), referring to the large body.
Gender feminine.
Type material. Holotype: female, specimen no.
CNU-ARC-MA-2014003.
Locality and horizon. Hukawng Village, Kachin
State, Northern Myanmar; Late Cretaceous.
Diagnosis. Body reaching to 6 mm; antenna shorter
than body length; distal chains of flagellum with about
12–15 subarticles; the distal segment of labial palps
slightly broadened than the second segment.
Taphonomic features. CNU-ARC-MA-2014003:
head, thorax and abdomen trapped in amber; numer-
ous bubbles surround body; antennae, maxillary palps
and legs complete; caudal appendages missing.
Description. Body: Body light brown, about 6 mm.
Head: Eyes large and touching at the medial line,
ocelli not recognizable. Antenna (Fig. 1e, g) shorter
than body length; scapus cylindrical, about 2 9as
long as wide, with several setae; pedicellus slightly
wider and longer than each segment of flagellum; flag-
ellum of the antennae dark brown, the most distal
chains of flagellum with 12–15 subarticles. Maxillary
palps 7-segmented (Fig. 1b, f), with long and slender
hairs, the basal segment with a triangular process and
a longitudinal process, the second segment without a
hook-like projection in female, apical segment some-
what pointed distally, and slightly shorter than the
penultimate segment. Labial palps 3-segmented
(Fig. 1h), the second segment longest, distal segment
longer than wide, slightly swollen.
Thorax: Thorax wider than abdomen. Legs clothed
with brown hair setae. Foreleg (Fig. 1d, i): trochanter
extremely long, even longer than femur, femur not
widened, tibia subequal to tarsus; middle leg (Fig. 1d,
j): trochanter slightly shorter than femur, femur nearly
Zhang et al. / Cladistics 0 (2017) 1–23 5

1.2 9as long as tibia, tibia slightly longer than tarsus;
hind leg (Fig. 1d, k): trochanter nearly 0.8 9as long
as femur, femur 1.2 9as long as tibia, tibia subequal
to tarsus. Middle and hind legs with coxal stylets. All
tarsi comprising three tarsomeres (Fig. 1c), ending in
paired claws.
Abdomen: Abdominal ventral plate consisting of a
small sternite (Fig. 1l). Stylets present on coxites II–
IX, terminal spine of stylet nearly half the stylet
length. Single eversible vesicle present on coxites II, IV
and V; eversible vesicles on other abdominal segment
hard to discern. Central caudal filament and two lat-
eral cerci not preserved. Ovipositor extending beyond
the end of stylets IX, of tertiary or quaternary type.
Remarks. It is clear that this species can be assigned
to the family Meinertellidae based mainly on its dorsal
basis of maxillary palps with a longitudinal projection
and small abdominal sternites. The new species pos-
sesses some typical Cretaceomachilis characters such as
distal segment of labial palps longer than wide, slightly
swollen; both middle and hind legs with coxal stylets;
tarsi 3-segmented. Cretaceomachilis libanensis, from the
Lower Cretaceous (120–135 Ma) Lebanese amber, is
the only species reported within Cretaceomachilis previ-
ously. The new species differs from C. libanensis in the
following characters: (i) C. longa (6 mm long) larger
than C. libanensis (4.5 mm long); (ii) antenna shorter
than body length (vs. antenna longer than body).
(a)
(b)
(d)
(c)
(e)
(f) (g)
(h)
(i) (j)
(k)
(l)
Fig. 1. Cretaceomachilis longa sp.n., holotype, CNU-ARC-MA-2014003. (a–e) Photographs: (a) overall habitus; (b) maxillary palps; (c) tarsus of
foreleg; (d) legs; (e) distal part of antenna. (f–k) Line drawings: (f) maxillary palps; (g) basal part of antenna; (h) labial palp; (i) foreleg; (j) mid-
dle leg with coxal stylet; (k) hind leg with coxal stylet; (l) coxosternite-V. ast, abdominal stylet; cst, coxal stylet; cv, coxal vesicle; fl, foreleg; hl,
hind leg; lop, longitudinal process; ml, middle leg; tp, triangular process. [Colour figure can be viewed at wileyonlinelibrary.com]
6Zhang et al. / Cladistics 0 (2017) 1–23

Genus Unimeinertellus gen.n.
Type species. Unimeinertellus abundus sp.n.
Etymology. The generic name is from Latin, combin-
ing “uni-” (single) in reference to one pair of stylets
present on legs, and “meinertellus” deriving from the
type genus of Meinertellidae. Gender masculine.
Diagnosis. Body about 4–6 mm long. Distal segment
of labial palps distinctly elongate; foreleg slightly
widened; only hind legs with coxal stylets; tarsi with
two tarsomeres. Ovipositor of tertiary type.
Remarks. Affiliation with Meinertellidae is sup-
ported by: (i) maxillary palps of male with a hook-like
projection on the second segment; (ii) tarsi with two
tarsomeres; (iii) abdominal sternites small; (iv) param-
era absent.
Unimeinertellus gen.n. is similar to cf. Macropsontus
Silvestri, 1911 (Mendes and Wunderlich, 2013) in tarsi
with two tarsomeres, but differs from it in its hind legs
with coxal stylets (vs. all legs devoid of coxal stylets).
Unimeinertellus gen.n. can be distinguished from Cre-
taceomachilis by its middle leg without coxal stylet (vs.
middle leg with coxal stylet); tarsi with two tarsomeres
(vs. three tarsomeres). Unimeinertellus gen.n. is slightly
larger than Vetmeinertellus gen.n., and the presence of
coxal stylets on hind legs separates it from the latter.
The new genus is similar to the extant genus
Machilontus, with features such as only hind leg with
coxal stylet, tarsi with two tarsomeres and ovipositor
of tertiary type. But the new genus (about 4–6mm
long) is distinctly smaller than Machilontus (about 8–
11 mm), and eyes of the new genus are oval-shape,
1.5–1.9 9as long as wide, which differs from
Machilontus.
Unimeinertellus abundus sp.n.
(Figs 2, 3)
Type material. Holotype: female, specimen no.
CNU-ARC-MA-2014010. Paratypes: five females,
specimen no. CNU-ARC-MA-2014008, 2014009,
2014014, 2014015, 2014017 and three males, specimen
no. CNU-ARC-MA-2014016, 2014019, 2014020.
Etymology. The species name is derived from the
Latin word “abundus”, in reference to the relatively
greater number of specimens compared to other spe-
cies found in Myanmar amber.
Locality and horizon. Hukawng Village, Kachin
State, Northern Myanmar; Late Cretaceous.
Taphonomic features. CNU-ARC-MA-2014010: head,
thorax and abdomen trapped in amber; a few bubbles
near the head; maxillary palps and legs complete; the
tip of antennae missing; the central caudal filament bro-
ken from the terminalia of abdomen. CNU-ARC-MA-
2014008: antennae, maxillary palps, legs and caudal
appendages almost complete; a long and deep fracture
cuts the body at the end of abdomen; a large bubble on
one side of abdomen. CNU-ARC-MA-2014009: anten-
nae, maxillary palps and legs complete; the distal part
of caudal appendages missing; several bubbles and
plant fragments surrounding the body. CNU-ARC-
MA-2014014: antennae, maxillary palps and one foreleg
broken; ovipositor and caudal appendages preserved.
CNU-ARC-MA-2014015: one antenna and maxillary
palps complete; numerous bubbles surrounding the
body. CNU-ARC-MA-2014017: antennae, maxillary
palps and legs complete; caudal appendages missing;
basal part of ovipositor preserved; many bubbles sur-
rounding the body. CNU-ARC-MA-2014016: anten-
nae, maxillary palps, legs and caudal appendages
almost complete; a conspicuous amber fracture at the
thorax. CNU-ARC-MA-2014019: maxillary palps and
maxillary palps complete; antennae broken; numerous
plant and other insect fragments surrounding the body.
CNU-ARC-MA-2014020: antennae and terminal part
of maxillary palps missing; legs preserved; caudal
appendages broken.
Description. Female body length 5–6 mm; male
smaller than female, body length 4–5 mm. Body cov-
ered by brown dense scales. Head and appendages
devoid of scales.
Head: Eyes light brown in female, but with dark med-
ian pigmented area in male; very large, width of both
eyes about 0.8 9width of head; oval-shape, 1.5–
1.9 9as long as wide; eyes touching at the medial line,
with ratios of line contact to length 0.5–0.6 (Fig. 2b).
Ocelli sole-shaped. Antenna (Fig. 2l) subequal to body
length, without scales; scapus cylindrical, about 3.0 9
as long as wide; pedicellus wider than each segment of
flagellum; the most distal chains of flagellum with about
17 subarticles (Fig. 3f). Maxillary palps 7-segmented,
with black strong setae; the apical segment somewhat
pointed distally, and slightly shorter than the penulti-
mate segment. The second segment of maxillary palps
in male with dorsal hook-like projection, the hook-like
projection extremely long, straight basally and slightly
curved at the apex (Figs 2g, 3c); female without hook-
like projection (Fig. 2d, f). Labial palps 3-segmented
(Figs 2h, 3d), with setulae, the distal segment elongate,
nearly 4.0 9as long as wide, and subequal to or
slightly longer than the second segment.
Thorax: Thorax slightly wider than abdomen; the
anterior angles of pronotum protracted and pointed;
mesothorax humped, and 2.1 9as long as prothorax,
and 1.6 9as long as metathorax. Forefemur slightly
thicker than middle and hind femora (Fig. 2c, i); mid-
dle leg without coxal stylet (Fig. 2c, j); hind leg with
coxal stylet (Fig. 2e, k). All tarsi comprise two tar-
someres, ending in paired claws.
Abdomen: Sternite small, difficult to discern. Stylets
present on coxite II–IX, the terminal spine of stylet
shorter than half the stylet length. At most one eversi-
ble vesicle on each coxite II–VII. Abdomen terminat-
ing in one central caudal filament and two lateral
cerci; central filament 1.1–1.2 9as long as body, and
Zhang et al. / Cladistics 0 (2017) 1–23 7

2.7–3.0 9as long as cerci. In females, ovipositor of
tertiary type, extending beyond the ending of stylets
IX (Fig. 3g). In males, paramera absent.
Remarks. On specimen CNU-ARC-MA-2014008,
two small spines present on the distal portion of the
hind femur (Fig. 3e), these spines being invisible on
the other specimens. Considering the great similarity
between CNU-ARC-MA-2014008 and other speci-
mens, we believe they should be the same species.
Unimeinertellus bellus sp.n.
(Figs 4–6)
Type material. Holotype: female, specimen no.
CNU-ARC-MA-2014001. Paratypes: one female, spec-
imen no. CNU-ARC-MA-2014007; one male, speci-
men no. CNU-ARC-MA-2014002.
Locality and horizon. Hukawng Village, Kachin
State, Northern Myanmar; Late Cretaceous [Cenoma-
nian].
(a) (b)
(c)
(d)
(e)
(f) (g)
(h)
(i)
(j)
(k)
(l)
Fig. 2. Unimeinertellus abundus gen. et sp.n. (a–e) Photographs, holotype, CNU-ARC-MA-2014010, female: (a) overall habitus; (b) eyes; (c) fore-
and middle legs; (d) maxillary palps; (e) hind leg. (f–l) Line drawings. (f, i–k, l) Holotype, CNU-ARC-MA-2014010: (f) female maxillary palp; (i) fore-
leg; (j) middle leg; (k) hind leg with coxal stylet; (l) basal part of antenna. (g) Male maxillary palp with hook-like projection, paratype, CNU-ARC-
MA-2014016. (h) Labial palp, paratype, CNU-ARC-MA-2014009. hp, hook-like projection. [Colour figure can be viewed at wileyonlinelibrary.com]
8Zhang et al. / Cladistics 0 (2017) 1–23

Etymology. The species name is derived from the
Latin word “bellus” (delicate), reflecting the small and
delicate body of the specimens.
Diagnosis. Antenna longer than body. The hook-like
projection on the second segment of maxillary palp
relatively short.
Taphonomic features. CNU-ARC-MA-2014001:
head, thorax and abdomen trapped in amber; two
antennae broken into six fragments; maxillary palps,
legs and caudal appendages almost complete; abun-
dant scales spreading everywhere. CNU-ARC-MA-
2014007: antennae, maxillary palps, legs and caudal
appendages complete; several fractures and impurities
near the body. CNU-ARC-MA-2014002: trapped in
the same amber with CNU-ARC-MA-2014001; anten-
nae and caudal appendages complete; part of maxil-
lary palp falling off; legs poorly preserved.
Description. Colour of body reddish brown.
Female. Body very small. Scales present on the
body.
Head: Eyes light coloured, large and round, length
subequal to width, partially contiguous, contact length
about 2/3 length of eye (Fig. 5b); ocelli not recogniz-
able. Antenna nearly 1.2 9as long as the body length,
with long setae; scapus cylindrical (Fig. 4b, g), about
2.0–2.4 9as long as wide; pedicellus and flagellum
completely devoid of scales; jointlets of flagellum
clearly discernible, the distal chains of flagellum with
nine subarticles (Fig. 4d). Maxillary palps (Figs 4b, f,
5b) well-developed, with seven segments covered by
thin and small light brown setae; the second segment
of maxillary palps without hook, the third segment
longest; the distal segment conical, and slightly shorter
than the penultimate one. Labial palps with three seg-
ments (Fig, 4b, f), the distal segment not broadened,
and shorter than the penultimate one.
Thorax: Thorax not very humped. Coxal stylets dif-
ficult to discern, tarsi with only two tarsomeres
(Figs 4c, 5c), lacking tarsal scopula, ending in paired
claws.
(a)
(b)
(d) (e)
(g)
(f)
(c)
Fig. 3. Unimeinertellus abundus gen. et sp.n., photographs, paratype. (a–c) CNU-ARC-MA-2014020: (a) overall habitus, dorsal view; (b) overall
habitus, ventral view; (c) male maxillary palps with hook-like projection. (d) Labial palps, CNU-ARC-MA-2014009. (e) Hind leg, CNU-ARC-
MA-2014008. (f) Distal chains of antennal flagellum, CNU-ARC-MA-2014009. (g) Coxosternite IX and ovipositor, CNU-ARC-MA-2014014.
ast-IX, abdominal stylet-IX; ce, cercus; hp, hook-like projection; ov, ovipositor. [Colour figure can be viewed at wileyonlinelibrary.com]
Zhang et al. / Cladistics 0 (2017) 1–23 9

Abdomen: Sternite not clear, possibly small; exser-
tile vesicle invisible; stylets present on coxite II–IX,
stylets with spinule. Abdomen terminating in three
long filaments; central caudal filament 1.5 9as long
as body, and 3.0 9as long as the lateral cerci.
Ovipositor of tertiary type, extending beyond the end
of stylets IX.
Male. Body 4.0 9as long as wide. Eyes grey and
round. Antenna nearly 1.5 9as long as the body
length, jointlets of flagellum clearly discernible, the dis-
tal chains of flagellum with 12 subarticles (Fig. 6c),
each subarticles with setae. Maxillary palps in male
with dorsal hook-like projection, the hook-like projec-
tion relatively short and slightly curved at the apex
(Fig. 6f). Labial palps not preserved. The boundaries
between pro-, meso- and metanotum obscure. Metan-
otum longer than pro- and mesonotum. Hind legs with
coxal stylets. Central caudal filament 1.9 9as long as
body, and 3.1 9as long as the lateral cerci.
Remarks. Considering the small size of these three
specimens, we speculate that they are probably imma-
ture. The species can be assigned to Unimeinertellus
gen.n., based on the following combination of charac-
ters: distal segment of labial palps elongate, hind legs
with coxal stylets, tarsi with two tarsomeres, and
ovipositor of tertiary type. Compared to U. abundus
sp.n.,U. bellus differs from it in: (i) antenna longer
than body (vs. antenna subequal or slightly shorter
than body); (ii) the hook-like projection relatively
short and stout (vs. extremely long and thin).
Genus Nullmeinertellus gen.n.
Type species. Nullmeinertellus wenxuani sp.n.
Etymology. The generic name is from the Latin by
combining “null-” (none) in reference to its legs devoid
(a)
(b)
(d)
(c)
(e)
(f)
(g)
Fig. 4. Unimeinertellus bellus sp.n., holotype, CNU-ARC-MA-2014001. (a–d) photographs: (a) overall habitus, lateral view; (b) female maxillary
palps and labial palps; (c) foreleg; (d) distal chains of antennal flagellum. (e–g) Line drawings: (e) habitus; (f) maxillary palp and labial palp; (g)
basal part of antenna. lp, labial palp; mp, maxillary palp. [Colour figure can be viewed at wileyonlinelibrary.com]
10 Zhang et al. / Cladistics 0 (2017) 1–23

of coxal stylets, and “meinertellus”, deriving from the
type genus of Meinertellidae.
Diagnosis. Body in medium size, about 6.5 mm;
antenna shorter than body; the distal segment of labial
palp elongate; all legs devoid of coxal stylets; foreleg
not thickened; tarsi with three tarsomeres.
Remarks. Nullmeinertellus gen.n. can be assigned to
Meinertellidae by its antenna without scales and legs
devoid of coxal stylets. Nullmeinertellus gen.n. is simi-
lar to Cretaceomachilis in tarsi with three tarsomeres,
but differs from the latter in its middle and hind legs
without coxal stylets. Compared with Unimeinertellus
gen.n.,Nullmeinertellus gen.n. differs distinctly from it
in its hind legs without coxal stylets (Unimeinertellus
gen.n. with coxal stylets on hind legs) and tarsi with
three tarsomeres (Unimeinertellus gen.n. possesses only
two tarsomeres).
Nullmeinertellus wenxuani sp.n.
(Fig. 7)
Type material. Holotype, female, specimen no.
CNU-ARC-MA-2014004. Paratype, larva, specimen
no. CNU-ARC-MA-2014005.
Type locality and horizon. Hukawng Village, Kachin
State, Northern Myanmar; Late Cretaceous [Cenoma-
nian].
Etymology. The specific name is dedicated to Wenx-
uan Li, the nephew of Mr. Jun Li who donated amber
specimens for our research.
Taphonomic features. CNU-ARC-MA-2014004:
antennae, maxillary palps and two lateral cerci com-
plete; central caudal filament partly preserved; a big
bubble near thorax; plenty of plant fragments and
impurities surrounding the body. CNU-ARC-MA-
2014005: trapped in the same amber with CNU-ARC-
MA-2014004; antennae complete; legs and caudal
appendages partly preserved; plenty of impurities sur-
rounding the body.
Description. Adult. Body dark brown, with irides-
cent colour scales, medium-sized (about 6.5 mm).
Head: Eyes grey, round and touching at the medial
line, ocelli not recognizable. Antenna about 0.8 9as
long as body, scapus cylindrical with long setae
(Fig. 7e, l), and about 1.3 9as long as wide; the most
distal chains of flagellum with about 12 subarticles.
Maxillary palps 7-segmented (Fig. 7c, h), with rela-
tively long setae; the second segment without hook-like
projection in female. Labial palps 3-segmented, the
basal segment shortest, the distal segment elongate,
subequal to the second segment, and 3.1 9as long as
wide (Fig. 7i).
Thorax: Thorax covered by scales dorsally. Thorax
wider than abdomen. Prothorax shortest, about
0.48 9as long as mesothorax and 0.86 9as long as
metathorax; the lateral margins of mesonotum diver-
gent posteriorly. Legs light brown, with dark brown
setae; foretibiae not thickened; middle and hind legs
without coxal stylets; all tarsi comprising three tar-
someres (Fig. 7d), and with two claws, lacking scop-
ula.
Abdomen: The lateral margins of abdominal tergites
I–III divergent posterior. coxosternite II, III with
acutely angled sternite, and large coxites meeting medi-
ally (Fig. 7j); other sternites invisible. Stylets present
on urosternites II–IX. The terminal spine of stylet-IX
(a)
(b)
(c)
Fig. 5. Unimeinertellus bellus sp.n., photographs, paratype, CNU-
ARC-MA-2014007: (a) overall habitus, dorsal view; (b) female max-
illary palp and eyes; (c) tibia and tarsi of foreleg. [Colour figure can
be viewed at wileyonlinelibrary.com]
Zhang et al. / Cladistics 0 (2017) 1–23 11

shorter than half the stylet-IX length (Fig. 7k). Eversi-
ble vesicles hard to discern. Central caudal filament
partly preserved, two lateral cerci 0.4 9as long as
body (Fig. 7k).
Larva. Body length 2.2 mm. Eyes round and touch-
ing at the medial line. Antenna 0.8 9as long as the
body length (Fig. 7g), scapus cylindrical, with setae;
pedicel wider and longer than each segment of fila-
ment. Maxillary palps 7-segmented. Foreleg longest,
and hind leg shortest. Middle and hind legs without
coxal stylets. Stylets present on urosternites II–IX,
sternite undeveloped. Caudal filament partly pre-
served.
Remarks. This is the first time that both larva and
adult of Archaeognatha have been found together in
one piece of amber. The larva is very similar to the
adult, which indicates that Archaeognatha in the
Mesozoic probably exhibited epimorphic development
as do extant species.
Adult body lengths of Archaeognatha range from
5 mm to 23 mm (Sturm and Bach de Roca, 1993). In
this study, we speculated that our specimens CNU-
ARC-MA-2014001, 2014002, 2014005 and 2014007
with the body lengths <4.0 mm (Table 2), are proba-
bly immature, but their specific larval instars are diffi-
cult to determine.
Phylogenetic results from MP analysis based on
morphological characters
The maximum parsimony analysis yielded 20 equally
most parsimonious trees (tree length =82 steps, con-
sistency index (CI) =0.59, retention index (RI) =0.78,
Fig. 8). Bremer’s decay index values are relatively low
(a)
(b) (c)
(e)
(d)
(f)
Fig. 6. Unimeinertellus bellus sp.n., paratype, CNU-ARC-MA-2014002. (a–c) Photographs: (a) overall habitus, dorsal view; (b) the last three seg-
ment of male maxillary palp and part of central caudal filament; (c) distal part of antenna. (d–f) Line drawings: (d) overall habitus, dorsal view;
(e) male maxillary palp; (f) hook-like projection. [Colour figure can be viewed at wileyonlinelibrary.com]
12 Zhang et al. / Cladistics 0 (2017) 1–23

throughout the tree (mostly in the range 1–2), and
they are presented on the node to which they relate
(Fig. 9).
Archaeognatha were recovered as a strongly mono-
phyletic group supported in this analysis by multiple
apomorphic characters, including compound eyes very
large (character 5: state 1); ectognathous mouthparts
(10:1); maxillary palp developed (11:1) and thorax
strongly arched (17:1). Note that ectognathous mouth-
parts is not an apomorphy of the Archaeognatha only.
It is an apomorphy of true insects (Archaeognatha +
Zygentoma +Pterygota), although ectognathous
mouthparts present an apomorphic character of
Archaeognatha in the cladogram (Fig. 8) due to the
choice of two entognathous outgroups.
The extinct Monura (Dasyleptidae) surviving from
the Early Devonian to the Triassic are the oldest taxa
within Archaeognatha. MP analysis shows that Mon-
ura are placed at the basal position represent the sister
group of Machiloidea. The annulated abdominal sty-
lets were reported in some fossil specimens of Monura
(Durden, 1978; Rasnitsyn, 1999), whereas the recent
(a)
(e)
(b)
(c) (d) (f)
(g)
(j)
(k)
(h)
(i)
(l)
(m)
Fig. 7. Nullmeinertellus wenxuani gen. et sp.n..(a–g) Photographs. (a–e) Holotype, CNU-ARC-MA-2014004: (a) overall habitus, ventral view;
(b) overall habitus, dorsal view; (c) female maxillary palp; (d) tibia and tarsi of foreleg; (e) basal part of antenna. (f–g) Paratype, CNU-ARC-
MA-2014005: (f) larval habitus; (g) basal part of larval antenna. (h–m) Line drawings, holotype, CNU-ARC-MA-2014004: (h) female maxillary
palp; (i) labial palp; (j) coxosternite III; (k) coxosternite IX, central caudal filament and two lateral cerci; (l) basal part of antenna; (m) foreleg.
ast-III, abdominal stylet-III; ast-IX, abdominal stylet-IX; cv, coxal vesicle. [Colour figure can be viewed at wileyonlinelibrary.com]
Zhang et al. / Cladistics 0 (2017) 1–23 13

Machiloidea, even other apterygote insects, have
abdominal stylets without annulation (Bechly and
Stockar, 2011). Thus, as the result of our phylogenetic
analyses, abdominal stylet annulated (24:0) is probably
a potential synapomorphy of the monuran species.
The monophyly of Machiloidea is supported by the
following synapomorphies: body covered by scales
(1:1); coxal stylets present on both middle and hind
legs (19:0), tarsi 3-segmented (20:1), and abdominal
stylet present, but absent on coxite I (23:2). Bremer’s
decay index was calculated for this clade as 3.
The phylogenetic positions of Petrobiellus and
Ditrigoniophthalmus are unresolved. The strict
consensus tree shows that Machilidae excluding
Ditrigoniophthalmus and Petrobiellus form a clade by
scales absent on flagellum of antenna (2:1) and scales
present on maxillary and labial palps, legs and stylets
(3:0). Kaplin (1985) divided Machilidae into three sub-
families, Petrobiinae, Petrobiellinae and Machilinae,
according to their grade of scale covering on antenna.
But Sturm and Bach de Roca (1993) thought this sub-
division was not all satisfactory, and recent molecular
phylogenetic analyses implied tangled relationships
among these subfamilies (Ma et al., 2015). In our
results, the monophyly of Petrobiinae is not confirmed.
Machilinae with Mesomachilis, Charimachilis and
Table 2
Length measurements (in mm) of the specimens described in this study
Body Antenna Caudal filament Cercus
Cretaceomachilis longa sp.n.
CNU-ARC-MA-2014003 6.0 5.4 ? ?
Unimeinertellus abundus gen. et sp.n.
CNU-ARC-MA-2014008 5.1 5.1 6.0 2.6
CNU-ARC-MA-2014009 5.0 5.0 >1.2 1.8
CNU-ARC-MA-2014010 5.0 >4.3 6.0 2.2
CNU-ARC-MA-2014014 5.0 >2.2 >4.6 2.6
CNU-ARC-MA-2014015 5.5 >3.2 >5.8 2.3
CNU-ARC-MA-2014016 4.0 3.8 4.8 1.6
CNU-ARC-MA-2014017 6.0 6.3 ? ?
CNU-ARC-MA-2014019 5.1 >1.2 >5.2 2.2
CNU-ARC-MA-2014020 4.5 ? >2.0 1.9
Unimeinertellus bellus sp.n.
CNU-ARC-MA-2014001 3.1 3.9 4.8 1.4
CNU-ARC-MA-2014002 3.7 6.0 7.1 2.3
CNU-ARC-MA-2014007 3.1 3.8 4.9 1.5
Nullmeinertellus wenxuani gen. et sp.n.
CNU-ARC-MA-2014004 6.5 5.2 >3.5 2.6
CNU-ARC-MA-2014005 2.2 1.8 ? ?
Fig. 8. Phylogeny of Archaeognatha recovered from the Maximum parsimony analysis. (a–c) three of 20 equally the most parsimonious trees
with characters and character states mapped. (●) nonhomoplasious; (○) homoplasious; (†) fossils.
14 Zhang et al. / Cladistics 0 (2017) 1–23

Turquimachilis included is recovered as a monophylum
with moderate support (Bremer support: 1) and one
synapomorphy: scales present on both pedicellus and
flagellum of antenna (2:0).
Meinertellidae is a monophyletic group that is sup-
ported by longitudinal projection present on the basal
segment of maxillary palp (12:1); hook-like projection
present on the second segment of maxillary palp in
male (13:1), the first segment of maxillary palps with
two inner humps (14:2), abdominal sternite small
(22:1), penis shorter than half length of coxite IX
(30:1) and penis aperture subapical, triangular (31:2).
Three fossil genera Cretaceomachilis,Unimeinertellus
gen.n. and Nullmeinertellus gen.n. are included in this
group. Unimeinertellus gen.n. has a close relationship
with Machilinus. However, Neomachilellus szeptyckii
forms a paraphyletic relationship with N. dominicanus.
This is probably due to poor preservation of the fossil
specimen of N. dominicanus that lacks sufficient infor-
mation to clarify its position.
Phylogenetic results from BI analysis based on total
evidence (morphology +molecular data)
Phylogenetic results from BI analysis involve mor-
phological data from both living and fossil taxa and
molecular data for the living taxa (Fig. 10). The com-
bined analysis can improve our understanding of rela-
tionships among taxa within Archaeognatha.
Archaeognatha is recovered as a monophyletic group
with strong statistical support (PP: 1.00) based on a
total-evidence dataset. Monura was recovered with
weak statistical support (PP: 0.62), and was a sister
group of the monophyletic group Machiloidea.
Ditrigoniophthalmus and Petrobiellus have a close rela-
tionship. Unexpectedly, they are detached from
Machilidae, and sister to the clade of Meinertellidae
with weak statistical support (PP: 0.64). Machilidae
sensu Remington turned out to be a paraphyletic
group. Charimachilis,Mesomachilis,Turquimachilis
and representatives of Machilinae and Petrobiinae
form a clade with high support (PP: 0.90). This differs
from the results achieved based on morphological
data, Machilinae was recovered as a paraphyletic
group. The monophyly of Petrobiinae just has very
weak statistical support (PP: 0.42). Meinertellidae is a
monophyletic group, which is supported by high statis-
tical support (PP: 0.99).
Discussion
Relationships among taxa of Archaeognatha
‘paleo-types’. Two different phylogenetic positions
of Ditrigoniophthalmus present in 20 equally most
parsimonious trees (MPTs). In some MPTs (Fig. 8b, c),
Ditrigoniophthalmus is recovered as a basal group of
Machiloidea, with the remaining Machiloidea forming
a monophyletic group that is supported by their
synapomorphy: the absence of stylet on coxite I. In
other MPTs (Fig. 8a), Ditrigoniophthalmus together
with the representatives of Machilidae form a clade
supported by the synapomorphy: paramere only
present on abdominal segment IX. Although
Ditrigoniophthalmus is almost universally considered as
the basal group to all of machiloids (Koch, 2003), our
results indicate that the phylogenetic position of
Ditrigoniophthalmus is still pending as reflected in the
strict consensus tree based on morphological data
(Fig. 9). Unlike the MP results, Ditrigoniophthalmus is
sister to Petrobiellus in the BI analysis based on the
combined data of morphology and DNA sequences
(Fig. 10). This result confirms the viewpoint of Kaplin
(1985) who assigned Ditrigoniophthalmus to
Petrobiellinae on the basis of unscaled antennae
which it shares with the genus Petrobiellus (Sturm and
Bach de Roca, 1993). Unexpectedly, the clade
Ditrigoniophthalmus + Petrobiellus is close to the
representatives of Meinertellidae, but the statistical
support is not high (Fig. 10). In consideration of the
different results of these two phylogenetic methods,
our studies do not clearly resolve the position of
Ditrigoniophthalmus.
Our results regarding other ‘paleo-types’ corroborate
the results of Koch (2003). Mesomachilis is well estab-
lished by distal articles of gonapophyses tapered pos-
teromediad and unique structure of penis. Although
Mesomachilis possesses its own specialized characters,
it shares some characters with machilids, such as pres-
ence of scales on the antenna and a well-developed
sternite. Consistent with the viewpoint of Bach de
Roca et al. (2013), Turquimachilis is close to Chari-
machilis in our results. Both of these two genera were
nested in Machilidae. Based on the available data, we
tentatively put ‘paleo-types’ excluding Ditrigoniophthal-
mus in Machilidae. Nonetheless, pending more speci-
mens being discovered and studies in the future, the
position of the ‘paleo-types’ needs to be confirmed.
Machilidae. The monophyly of Machilidae remains
questionable (Koch, 2003). Both of these two results
show that Machilidae sensu Remington is a
paraphyletic group. Petrobiellus is a sole genus of
Petrobiellinae. The genus shares an apomorphic feature
with the Petrobius group: weak and indistinct
separation of the distal mandibular teeth, based on
which Sturm and Bach de Roca (1993) suggested that
the Petrobius group and Petrobiellus evolved from the
same ancestor or that a parallel evolution took place.
However, Petrobiellus also possesses the evolved
character, scale absent on antenna, maxillary and labial
Zhang et al. / Cladistics 0 (2017) 1–23 15

palps, legs and stylet (present in meinertellids). Thus,
the position of Petrobiellus is not resolved well by MP
analysis. Ma et al. (2015) conducted phylogenetic
analyses of Archaeognatha using concatenated
nucleotide sequences with four different computational
algorithms. In most of their results, Petrobiellus is close
to meinertellids. We combine morphological and
molecular data, and obtain a similar result to that of
Ma et al. (2015). So, the previous classification with
Petrobiellus nested in Machilidae is challenged. The
two results supporting the monophylies of Petrobiinae
and Machilinae are different: based on morphological
characters, Machilinae recovered as a monophylum,
whereas Petrobiinae is a paraphyletic group; however,
the BI analysis based on total evidence retrieved the
opposite result. Thus, the division of these three
subfamilies proposed by Kaplin (1985) seems to be
lacking adequate evidence.
Meinertellidae. Meinertellidae possess several
synapomorphies that support the monophyly of this
family. Consistent with the universal view, both MP
and BI results indicate that Meinertellidae is a
monophyletic group with high Bremer support and
posterior probability. Due to the relatively high
uniformity of Meinertellidae, this family is not divided
into subfamilies, but instead four genus groups were
proposed (Sturm and Bach de Roca, 1993):
Fig. 9. Phylogeny of Archaeognatha recovered from the Maximum parsimony analysis. The strict consensus tree with Bremer support values
mapped. (†) fossils. [Colour figure can be viewed at wileyonlinelibrary.com]
16 Zhang et al. / Cladistics 0 (2017) 1–23

Machiloides,Hypomachiloides,Machilontus and
Meinertellus groups. The extinct Unimeinertellus gen.n.
presents a close relationship with the Machilontus
group supported by coxal stylets present only on hind
leg (19:1) and tarsi with two segments (20:0).
Divergence of Machilidae and Meinertellidae, and the
origin of Meinertellidae
Sturm and Poinar (1998) reported the oldest mein-
ertellids, Cretaceomachilis. Based on this finding, they
suggested that the separation of the Meinertellidae
from the other representatives of the Archaeognatha
was completed or nearly completed by the Early Cre-
taceous epoch (Sturm and Poinar, 1998). According to
the new findings in the present study, Cretaceous
meinertellids still possess many primitive characters,
such as antenna as long as the body and distal seg-
ment of labial palps elongate, but several derived char-
acters have evolved, such as reduction of coxal stylets
(Unimeinertellus gen.n. with only a pair of coxal stylets
on hind leg; Nullmeinertellus gen.n. without coxal sty-
lets) and ovipositor of tertiary type. This fossil evi-
dence further indicates that the divergence time of
Machilidae and Meinertellidae is much earlier than the
Cretaceous. Machilidae bear more primitive structures,
and are considered to have originated earlier than
Meinertellidae (Sturm and Bach de Roca, 1993). How-
ever, the fossil record of Machilidae is very sparse.
Only one Cretaceous fossil record was mentioned by
Grimaldi et al. (2002), and the validity of this record
still needs further confirmation, due to the absence of
any description of this species. Until now, no fossil
Machilidae earlier than Cretaceous have been
reported. Therefore, future descriptions of the Meso-
zoic machilids will fill this gap and enhance our knowl-
edge of the evolution of Archaeognatha.
Two recent families present distinct geographical
patterns: Machilidae predominantly in the Northern
Hemisphere and Meinertellidae mostly in the Southern
Fig. 10. Phylogeny of Archaeognatha. Consensus tree recovered from Bayesian analysis of combined morphological characters and DNA
sequence data. Bayesian posterior probability values are included at nodes. (†) fossils. [Colour figure can be viewed at wileyonlinelibrary.com]
Zhang et al. / Cladistics 0 (2017) 1–23 17

Hemisphere (Mendes, 2002; Grimaldi and Engel,
2005). Based on the palaeogeographic map marked
with all the Archaeognatha fossil records (Fig. 11),
Palaeozoic Dasyleptidae have been found mainly in
the Northern Hemisphere and near the Equator; fur-
ther investigations and searches are needed from the
rest of the Earth to confirm their distribution. The
viewpoint of Sturm and Machida (2001) proposing a
Laurasian origin of Meinertellidae seems debatable.
The oldest known meinertellid is from Lebanese amber
(Sturm and Poinar, 1998). Lebanon is considered to be
in a northeastern position in the Gondwana continent
during the Early Cretaceous (Azar et al., 2003), which
suggests a Gondwanan origin for the Meinertellidae.
We also applied two approaches for inferring the ori-
gin of Meinertellidae. Based on the obtained total-evi-
dence phylogeny, we reconstructed the ancestral states
for the geographical distribution of Meinertellidae
using Mesquite: this group’s inferred ancestral distri-
bution was across the Oriental region and Oceania
(Fig. 12). However, the S-DIVA analysis locates the
ancestral distribution for Meinertellidae in either the
Arabian Peninsula, Oriental region, Oceania, South
America or the Arabian Peninsula, Oriental region,
Oceania, North America (Fig. 12). Combining these
two biogeographical analyses, we consider that the
Oriental region, Oceania and Arabian Peninsula are
the most likely places of origin. Due to the fact that
most of the landmasses in today’s Southern Hemi-
sphere, as well as the Oriental region and Arabian
Peninsula that have now moved entirely into the
Northern Hemisphere, belonged to Gondwana paleo-
geographically, we speculate that Meinertellidae origi-
nated from Gondwana, and then formed a dominant
Fig. 11. Historical biogeography and hypothetical phylogeny with fossil records. Palaeogeographic map I marked with the fossils from the
Devonian to Triassic, map II marked with the fossils from the Jurassic to Cretaceous, and map III marked with the fossils from the Cenozoic.
Letters in the circles on the right hand side represent the fossil records in Table 1. As Machilidae is probably a paraphyletic group, the branch is
indicated with dashes. [Colour figure can be viewed at wileyonlinelibrary.com]
18 Zhang et al. / Cladistics 0 (2017) 1–23

position in the Southern Hemisphere. With plate tec-
tonic changes, Meinertellidae expanded its distribution.
Sturm and Machida (2001) mentioned an Late Creta-
ceous meinertellid specimen from New Jersey amber
(USA), but without any detailed description. If this
were to be confirmed, it may indicate that some
ancient meinertellids migrated to North America
before the Cretaceous. Based on research in the Isth-
mus of Panama, Bacon et al. (2015) made a point that
the dramatic biotic turnover associated with the Great
American Biotic Interchange began as early as the
Oligocene–Miocene transition. The presence of Neo-
machilellus in Miocene amber of the Dominican
Republic and Mexico (Sturm and Poinar, 1997;
Riquelme et al., 2015) may indicate that meinertellids
migrated from South America to North America via
the Isthmus of Panama. The fossil record may eventu-
ally provide direct evidence to clarify and reconstruct
this pattern of dispersal, but meinertellid fossils remain
limited without continued exploration.
Fig. 12. Historical biogeography of Meinertellidae. Results of Mesquite are indicated by coloured circles; results of Statistical Dispersal-Vicar-
iance Analysis (S-DIVA) are indicated by capital letters. Equally optimal ancestral distributions are indicated by pie-charts (Mesquite) or slashes
(S-DIVA). A, Asia excluding Arabian Peninsula and Oriental region; B, Arabian Peninsula; C, Oriental region; D, Europe; E, Africa; F, Ocea-
nia; G, South America; H, North America. [Colour figure can be viewed at wileyonlinelibrary.com]
Zhang et al. / Cladistics 0 (2017) 1–23 19

Conclusions
In our investigation, the morphology of archaeog-
nathan fossils is integrated with morphology and
DNA sequences of extant taxa to perform a ‘total evi-
dence’ phylogenetic analysis. It is the first attempt at
the phylogenetic study of taxa in Archaeognatha.
Combining the phylogenetic results based on morpho-
logical characters and total evidence, we reach the
following conclusions: (i) Meinertellidae are a mono-
phyletic group; (ii) Machilidae are probably a para-
phyletic group, but Machilidae excluding
Ditrigoniophthalmus and Petrobiellus form a clade; (iii)
The ‘paleo-types’ Charimachilis, Mesomachilis and
Turquimachilis are nested within Machilidae based on
the available data; (iv) The monophylies of Machilinae
and Petrobiinae are poorly resolved. Four new Creta-
ceous species of bristletails further indicate that the
divergence time of Machilidae and Meinertellidae is
much earlier than the Cretaceous. The possibility of a
Gondwanan origin of Meinertellidae is proposed.
Future discovery of new specimens in amber and com-
pression fossils from various geographical locations
and horizons, and the acquisition of further molecular
sequence data will contribute to refinements in knowl-
edge of origination, phylogenetic relationships and
evolutionary changes among the jumping bristletails
and their extinct relatives.
Acknowledgements
We appreciate constructive comments and sugges-
tions from the editor and two anonymous reviewers in
improving our manuscript. We thank Dr Mei Wang
(Chinese Academy of Forestry) for her helpful com-
ments. This research was supported by the National
Natural Science Foundation of China (Nos. 41402009,
31401991, 31672323 and 41688103), Natural Science
Foundation of Hebei Province (No. D2015403010),
Program for Changjiang Scholars and Innovative
Research Team in University (IRT17R75), and the
Chinese Universities Scientific Fund (Nos. 2016QC025,
2016QC072 and 2016ZB001).
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Supporting Information
Additional Supporting Information may be found in
the online version of this article:
Appendix S1. Character matrix, composed of 26
taxa and 34 characters.
Appendix S2. List of recent taxa and Genbank
accession numbers.
Appendix S3. Commands of MrBayes analysis based
on total evidence data of Archaeognatha.
Appendix 1
Morphological character descriptions and character
argumentation
1. Body: without scales (0); covered by scales (1).
2. Scales on antenna: scales present on both pedicellus and flag-
ellum (0); scales absent on flagellum (1); scales absent on pedi-
cellus and flagellum (2). [Scale covering antenna is considered
to be a plesiomorphic state (Sturm and Bach de Roca, 1993).
Antenna completely devoid of scale in Meinertellidae and
Petrobiellinae. Machilinae possess scales on scapus, pedicellus
and flagellum, whereas in Petrobiinae, scales only present on
scapus and pedicellus.]
3. Scales on maxillary and labial palps, legs and stylets: present
(0); absent (1).
4. Antenna: very short, not beyond thorax (0); shorter than or
as long as body length (1); longer than body (2). [Relatively
short antenna is the plesiomorphic state (Sturm and Bach de
Roca, 1993).]
5. Compound eyes: reduced or absent (0); very large (1).
6. Two compound eyes: not touching (0); contact dorsally (1).
[The compound eyes are large in Dasyleptidae, but they are
not touching.]
7. Eyes shape: round (0); oval (1); bean-shaped (2).
8. Lateral ocelli: absent (0); present (1).
9. Ocelli shape, and position corresponding to eyes: sole-shaped
(0); rounded to triangular, submedial position (1); rounded to
triangular, sublateral position (2). [Sole-shaped is considered
to be plesiomorphy on family level (Sturm and Bach de Roca,
1993). The reduction of the side edges of ocelli contributes to
the gradual formation of submedial or sublateral ocelli
(Kaplin, 1985).]
10. Mouthparts: entognathous (0); ectognathous (1).
11. Maxillary palp: highly reduced (0); developed (2). [Archaeog-
natha possesses very long maxillary palps. Most of machi-
loids have 7-segmented maxillary palps, except
Ditrigoniophthalmus with eight segments.]
12. Longitudinal projection (processus basalis): absent (0); pre-
sent on the basal segment of maxillary palp (1).
13. Hook-like projection: absent (0); present on the second seg-
ment of the maxillary palp in male (1). [Nearly all Meinertel-
lidae have hook-like projection on maxillary palp, but
Allomachilis lacks this structure.]
14. The first segment of maxillary palps: without inner hump (0);
with one inner hump (1); with two inner humps (2).
15. Distal segment of labial palp: elongate (0); broadened (1).
16. Mandible: with mandibular molar plate (0); with four dis-
tinct teeth (1); apical part of mandible without tooth or with
less than four distinct teeth (2).
17. Thorax: more or less flattened (0); strongly arched (1).
18. Forefemur of male: without sensory field (0); with opened
sensory field (1).
19. Coxal stylet: present on both middle and hind legs (0); pre-
sent only on hind leg (1); completely absent (2). [Most
machilids have two pairs of coxal stylets, but most meinertel-
lids devoid of coxal stylets. Coxal stylet appears the tendency
of reduction.]
20. Tarsi: with less than three segments (0); with three segments
(1). [Machilids always have 3-segmented tarsi, whereas a few
of meinertellids, such as Machilontus and Unimeinertellus
gen.n., have 2-segmented tarsi.]
21. Tarsi: with two claws (0); with one claw (1).
22. Abdominal sternite: large, broader than one of the corre-
sponding coxite and longer than 1/2 the length of one of
them (0); small, width at most 0.8 9width of one corre-
sponding coxite, length at most 0.35 9length of coxite (1).
[The definition criterion of small or large sternite refers to
Sturm and Bach de Roca (1993).]
23. Abdominal stylet: completely absent (0); present, including
on coxite I (1) present, but absent on coxite I (2). [Most of
jumping bristletails without stylet on coxite I. The presence
of stylet in Ditrigoniophthalmus separate it from all the other
extant jumping bristletails.]
24. Abdominal stylet: annulated (0); without annulation (1).
25. Eversible vesicle: at most one eversible vesicle on each coxite
II–VII (0); coxite II–V with two pairs of eversible vesicles
(1); coxite II–VI with two pairs of eversible vesicles (2). [The
presence of a single pair eversible vesicle should probably be
regarded as plesiomorphy (Kaplin, 1985).]
26. Lateral cerci: completely reduced (0); present (1).
27. Ovipositor: not extending beyond the ends of stylet-IX (0);
extending beyond the ends of stylet-IX (1).
28. Ovipositor type: primary type (0); secondary type (1); tertiary
type (2); quaternary type (3). [Ovipositor type refers to
Sturm and Bach de Roca (1993)]
29. Gonapophysis VIII and IX: < 40 articles (0); > 40 articles (1).
22 Zhang et al. / Cladistics 0 (2017) 1–23

30. Penis: longer than 1/2 length of coxite IX (0); shorter than
1/2 length of coxite IX (1). [In Meinertellidae, penis is
shorter than 1/2 length of coxite IX, which is considered
as a apomorphic character state (Sturm and Machida,
2001)]
31. Penis aperture: apical (0); subapical, round (1); subapical, tri-
angular (2); ventral, slit-like (3).
32. Paramere: absent (0); only present on abdominal segment IX
(1); present on abdominal segment VIII and IX (2).
33. Paramera IX: articulated (0); without articulated (1); highly
modified (2). [Charimachilis and Turquimachilis possess
highly modified paramera IX (Bach de Roca et al., 2013).]
34. Paramera IX: with tubular setae (0); without tubular setae
(1); highly modified (2).
Zhang et al. / Cladistics 0 (2017) 1–23 23