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The holotype of Dasyleptus brongniarti Sharov, 1957. Photo from Carpenter (1992, figure 11B), and reconstruction from Rasnitsyn (1999) figure 6 (based on the holotype plus several paratypes).
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... Monura are primitive wingless insects known as fossils from the Pennsylvanian and Permian strata (Tasch, 1973). They are united with their extant relatives the bristletails and silverfish by several char- acters: all are wingless, similar in size and form, have well developed antennae, ununited thoracic segments, and molt throughout their lifetimes (Carpenter, 1992). Rasnitsyn (1999) redescribed the monuran Dasyleptus brongniarti ( Fig. 1) and assembled a morphometric database of 25 specimens of the species. All the specimens are from the Kaltan locality in the Kuznetsk Formation of southwestern Siberia and are currently lo- cated at the Paleontological Institute, Russian Academy of Sciences, Moscow, Russia. The Kuznetsk Formation is Middle Permian (Ufimian) in age (Zhuravlev and Ilynia, 1988). Body lengths (excluding the caudal filament) of the 25 specimens are shown in Table 1. With this rela- tively large database, it was possible to use a statistical method to in- vestigate their growth characteristics. Thirty or more specimens would have been the preferred statistical sample size, but 25 specimens yielded a satisfactory result. We applied a probability plotting method to the body length data of these specimens to test for statistical size group- ings that could represent life stages between moltings (instars). A very brief explanation of the probability plotting method is included here. It is by no means comprehensive and only attempts to elaborate on the specifics pertinent to interpreting the D. brongniarti data. Probability plotting is a simple, powerful, graphic method of com- paring a data set to a statistical distribution function. A probability plot shows the probability (x axis) that a random observed variable will be less than or equal to a given value (y axis). Probability calculations are simple and the plots are easily made by hand, but here we used KaleidaGraph (1997) graphic analysis software to produce publication quality output. The probability data are plotted against a scale that is generated by a specific distribution function (e.g., normal, log normal, extreme, etc.). Straight line fits of the data to a specific probability scale indicate that the data are distributed according to the function used to generate that scale. Departures from a straight line fit indicate that the data are skewed, truncated, multi-modal, or do not fit the distribution function (King, 1971; Kock and Link, 1970). A normal (Gaussian) probability plot (Fig. 2A) of D. brongniarti body lengths has several “plateaus” that vary from horizontal to some- what inclined. These indicate that the overall distribution of body lengths comprises several component modes (King, 1971). A smooth curve drawn through the data points shows that the plateaus are connected by steep jogs that contain concave-up to concave-down inflections (pro- ceeding left to right). These inflection points indicate the approximate “boundaries” of the component distributions (Knoop and Owen, 1994; Peck, 1987). Theoretically, the distributions expand infinitely in either direction from the mean, but given a finite data set, the inflection points provide a very good approximation of the limits of each component mode. Only the concave-up to concave-down inflections are used to show the component mode boundaries; concave-down to concave-up inflections indicate the approximate mean of the components. We sepa- rate the overall distribution (Fig. 2A) into its six components at the inflection points (X’s in the figure) and replot each component (Fig. 2B). The straight line curve-fits to the components indicate that they have been correctly resolved and that they are normal (Peck, 1988). The uppermost component contains only two members and is, of course, a very rough approximation. The mean value and standard deviation (s) of each component may be read directly off the plot. The mean value occurs at the 50% probability point; +s and -s occur at the 84% and 16% probability points respectively (King, 1971). For greater accuracy, we used the coeffi- cients of the linear curve fits (Fig. 2B) provided by the graphic analysis software. Mean values and standard deviations of the resolved instars are given in Table 2. The mean values of the resolved instar sizes were used to generate a step plot (Fig. 3), which is a partial growth curve for D. brongniarti . The approximate instar numbers are assigned based on the similar- sized modern silverfish Lepisma saccarinum (Zygentoma: Lepismatidae) which is ~ 4.1 mm long in its fifth instar (Delaney, 1957) and attains an adult length of 15 to 20 mm. L. saccharinum has 11 to 13 pre-breeding instars (Sharov, 1953) and continues ecdysis as an adult, molting as many as 35 times in its 45 month lifetime (Larink, 1983). The resolved instars of D. brongniarti also fall within the range of the modern bristletail, Petrobius (Archaeognatha: Machilidae), which has seven to eight pre-breeding instars (Smith and Watson, 1991). The number of instars in D. brongniarti is unknown and may or may not exactly match those of Lepisma , nonetheless, a substantial segment of the pre-breeding growth curve of the animal has been reconstructed. The span of the retrieved growth curve is 3.5 to 12 mm and represents most of ...
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In het voorjaar van 2010 vond ik tijdens een bezoek aan de Piesberg-groeve bij Osnabrück, Duitsland een stamfragment van een paardenstaart met daarop enkele langwerpig-ovale structuren. Die markeringen waren zeker niet alledaags, maar destijds was verdere informatie onvindbaar en zodoende strandde het fossiel als ongeïdentificeerd in mijn verzameli...
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... Ideally, this involves directly measuring the frequency distribution of one or more metrics of exoskeleton size for each instar using laboratory-reared specimens with known molting status (e.g., based on molted head capsule dimensions) [22]. However, instar determination should be possible without knowledge of molting status if the number of developmental stages is known in advance, the morphometric data are uniformly sampled across all life stages, and the frequency distribution of these data is partitioned into distinct clusters [23]. The last approach is especially useful for SLFs, which have proven challenging to raise in the laboratory so that life stage can be directly monitored [20,21], and which we have observed to have flaccid cast exoskeletons that do not provide useful sizing information after molting. ...
A major ongoing research effort seeks to understand the behavior, ecology and control of the spotted lanternfly (SLF) (Lycorma delicatula), a highly invasive pest in the U.S. and South Korea. These insects undergo four nymphal stages (instars) before reaching adulthood, and appear to shift host plant preferences, feeding, dispersal and survival patterns, anti-predator behaviors, and response to traps and chemical controls with each stage. However, categorizing SLF life stage is challenging for the first three instars, which have the same coloration and shape. Here we present a dataset of body mass and length for SLF nymphs throughout two growing seasons and compare our results with previously-published ranges of instar body lengths. An analysis using two clustering methods revealed that 1st-3rd instar body mass and length fell into distinct clusters consistently between years, supporting using these metrics to stage nymphs during a single growing season. The length ranges for 2nd-4th instars agreed between years in our study, but differed from those reported by earlier studies for diverse locations, indicating that it is important to obtain these metrics relevant to a study’s region for most accurate staging. We also used these data to explore the scaling of SLF instar bodies during growth. SLF nymph body mass scaled with body length varied between isometry (constant shape) and growing somewhat faster than predicted by isometry in the two years studied. Using previously published data, we also found that SLF nymph adhesive footpad area varies in direct proportion to weight, suggesting that footpad adhesion is independent of nymphal stage, while their tarsal claws display positive allometry and hence disproportionately increasing grasp (mechanical adhesion). By contrast, mouthpart dimensions are weakly correlated with body length, consistent with predictions that these features should reflect preferred host plant characteristics rather than body size. We recommend future studies use the body mass vs length growth curve as a fitness benchmark to study how SLF instar development depends on factors such as hatch date, host plant, temperature, and geographic location, to further understanding of life history patterns that help prevent further spread of this invasive insect.
... The appearance of Apterygota and Pterygota in phyletic sequence is a particularly informative example due to the disparities in preservation potential among these two groups. The Pennsylvanian-Permian fossil record contains over 5500 described occurrences of Pterygota, but fewer than 20 described occurrences of apterygote insects (Durden, 1975;Rasnitsyn et al., 2004;Rinehart et al., 2005;Engel, 2009;Staniczek et al., 2014;Mendes, 2018;Liu et al., 2021). Because apterygote insects are so much less likely to become fossilized, their presence in the fossil record during an extended interval from which pterygotes are unknown can be reasonably interpreted as true evidence of pterygote absence. ...
The earliest fossils of winged insects (Pterygota) are mid-Carboniferous (latest Mississippian, 328-324 Mya), but estimates of their age based on fossil-calibrated molecular phylogenetic studies place their origin at 440-370 Mya during the Silurian or Devonian. This discrepancy would require that winged insects evaded fossilization for at least the first ~50 Myr of their history. Here, we examine the plausibility of such a gap in the fossil record, and possible explanations for it, based on comparisons with the fossil records of other arthropod groups, the distribution of first occurrence dates of pterygote families, phylogenetically informed simulations of the fossilization of Palaeozoic insects, and re-analysis of data presented by Misof and colleagues using updated fossil calibrations under a variety of prior probability settings. We do not find support for the mechanisms previously suggested to account for such an extended gap in the pterygote fossil record, including sampling bias, preservation bias, and body size. We suggest that inference of an early origin of Pterygota long prior to their first appearance in the fossil record is probably an analytical artefact of taxon sampling and choice of fossil calibration points, possibly compounded by heterogeneity in rates of sequence evolution or speciation, including radiations or 'bursts' during their early history.
... The appearance of Apterygota and Pterygota in phyletic sequence is a particularly informative example due to the disparities in preservation potential among these two groups. The Pennsylvanian-Permian fossil record contains over 5500 described occurrences of Pterygota, but fewer than 20 described occurrences of apterygote insects (Durden, 1975;Rasnitsyn et al., 2004;Rinehart et al., 2005;Engel, 2009;Staniczek et al., 2014;Mendes, 2018;Liu et al., 2021). Because apterygote insects are so much less likely to become fossilized, their presence in the fossil record during an extended interval from which pterygotes are unknown can be reasonably interpreted as true evidence of pterygote absence. ...
The earliest fossils of winged insects (Pterygota) are mid-Carboniferous (latest Mississippian, 328–324 Mya), but estimates of their age based on fossil-calibrated molecular phylogenetic studies place their origin at 440–370 Mya during the Silurian or Devonian. This discrepancy would require that winged insects evaded fossilization for at least the first ~50 Myr of their history. Here, we examine the plausibility of such a gap in the fossil record, and possible explanations for it, based on comparisons with the fossil records of other arthropod groups, the distribution of first occurrence dates of pterygote families, phylogenetically informed simulations of the fossilization of Palaeozoic insects, and re-analysis of data presented by Misof and colleagues using updated fossil calibrations under a variety of prior probability settings. We do not find support for the mechanisms previously suggested to account for such an extended gap in the pterygote fossil record, including sampling bias, preservation bias, and body size. We suggest that inference of an early origin of Pterygota long prior to their first appearance in the fossil record is probably an analytical artefact of taxon sampling and choice of fossil calibration points, possibly compounded by heterogeneity in rates of sequence evolution or speciation, including radiations or ‘bursts’ during their early history.
... The use of Dyar's rule ideally involves directly measuring the frequency distribution of one or more morphometric measures for each instar using specimens with known molting status (e.g., from measuring molted head capsule dimensions) (23). However, instar determination should be possible without knowledge of molting status if the number of developmental stages is known in advance, the morphometric data is uniformly sampled across all life stages, and its frequency distribution is partitioned into distinct clusters (24). The last approach is especially useful for SLFs, which have proven challenging to raise in the laboratory so that life stage can be directly monitored (20,21), and which we have observed to have flaccid cast exoskeletons that do not provide useful sizing information after molting. ...
A major ongoing research effort seeks to understand the behavior, ecology and control of the spotted lanternfly (SLF) ( Lycorma delicatula ), a highly-invasive pest in the U.S. and South Korea. These insects undergo four nymphal stages (instars) before reaching adulthood, and appear to shift host plant preferences, feeding, dispersal and survival patterns, anti-predator behaviors, and response to traps and chemical controls, with each stage. However, categorizing SLF lifestage is challenging for the first three instars, which have the same coloration and shape, because no comprehensive allometric datasets exist. We present a dataset of body mass and length for SLF nymphs throughout a growing season and compare our results with published ranges of instar body lengths based on small samples. An ontogenetic allometric analysis found that SLF nymph body mass scales isometrically with body length (exponent c = 3.05 [2.95,3.15]). An analysis using two clustering methods also revealed that first through third instar body mass and length fell into distinct clusters (Dyar’s rule), supporting using these two metrics to stage nymphs during a single growing season. The ranges for 2nd and 3rd instars were not consistent between our results and those from earlier studies for diverse locations. Using previously-published data, we also found that tarsal claw and arolia (adhesive footpad) dimensions scale in proportion to body length and mass, respectively, indicating that adhesive ability does not decrease with age, as posited in some previous studies. Conversely, mouthpart dimensions do not correlate with body length, consistent with predictions that these features should reflect preferred host plant characteristics rather than body size. We suggest extending these methods to study how SLF instar development depends on factors such as hatch date, host plant, temperature, and geographic location, using citizen scientist networks to collect morphometric data for a wide range of locations and environmental conditions.
... 1115 and figured in Minter and Braddy (2009, Fig. 25 C) is about 20 mm, which is comparable, although 30% shorter, to MBG 12503. These sizes are much larger than the average length documented by body fossils of late Paleozoic to Triassic dasyleptid bristletails, which have a BL of about 5-10 mm (e.g., Durden 1978;Rinehart et al. 2005;Engel 2009;Bechly and Stockar 2011). In extant bristletails, BL ranges from 6 mm to 25 mm (Gullan and Cranston 2014). ...
We describe a compound trace fossil Stiaria cf. intermedia C Avolatichnium isp. from the lower Permian of Southern Alps (North Italy) and confidently attribute it to a wingless (apterygote) jumping insect producer belonging to the order Monura (Insecta: Archaeognatha). We discuss the common features linking the ichnogenera Avolatichnium, Rotterodichnium and Tonganoxichnus, and suggest a close affinity for their producers. Grounded on previous studies and on some exceptional features preserved in the described material, we provide a biomechanical model for jumping in Archaeognatha and hypothesize that Paleozoic Archaeognatha performed jumps with high vertical and very low horizontal component and only later acquired the ability to heighten the horizontal component of their jumps, therefore, becoming more efficient in propelling themselves far ahead as extant species do.
... The palaeoecology of monurans was briefl y discussed by MÁNGANO et al. (2001) and SINITSHENKOVA (2003). RINEHART et al. (2005), who studied the ontogenesis of Dasyleptus brongniarti, could identify six instars with a very similar growth pattern (following Przibram's rule) as in Recent Archaeognatha and Zygentoma. ...
... Indeed, alone the type series of Dasyleptus lucasi includes 45 specimens from the Commentry basin (BITSCH & NEL 1999), which has been a tropical swamp in the Carboniferous. Furthermore, 10 specimens of Dasyleptus rowlandi are mentioned by RASNITSYN et al. (2004) from the late Carboniferous palaeolake of Carrizo Arroyo (ROWLAND 1997), andRINEHART et al. (2005) studied 25 specimens of Dasyleptus brongniarti from Siberia. Also the Archaeognatha-like ichnofossils from Carboniferous estuary deposits in Kansas andIndiana (MÁGNANO et al. 1997, 2001;BRADDY & BRIGGS 2002) and Permian deposits of Brazil (GUERRA-SOMMER et al. 1984) have been convincingly attributed to jumping monurans and suggest a way of life at the marine and brackish drift line and possibly also freshwater shores. ...
Dasyleptus triassicus n. sp. (Monura: Dasyleptidae) is described from the Ladinian (Middle Triassic) Meride Limestone of Monte San Giorgio in Switzerland. It is the first fossil record of an apterygote insect from the Trias-sic, and the first Mesozoic record of the extinct group Monura. Monurans were previously only known from the Palaeozoic Upper Carboniferous and Lower Permian. This new discovery shows that these delicate insects did sur¬vive the great end-Permian mass extinction event. Dasyleptus is considered to be a neotenic bristletail that lived at the drift line of sea shores and banks of freshwater bodies and swamps. A sister group relationship of Dasyleptidae with Ectognatha is rejected as insufficiently founded, and Monura is confirmed as a suborder of Archaeognatha, which represents the sister group of all Recent bristletails (suborder Machilida n. stat.). Fossil insects with unusual features, described from the Carboniferous of Mazon Creek as ‘Dasyleptus’ spec. by KUKALOVÁ-PECK, are here con¬sidered as “chimeras” from three different organisms: 1) genuine monurans; 2) Cercopodata; 3) stem group insects unrelated to Dasyleptidae but maybe congeneric with the alleged fossil silverfish Ramsdelpidion. Their status as genuine fossil evidence is supported and claims of “intensive preparation” rejected as insuffi ciently founded. K e y w o r d s : fossil insects, Archaeognatha, Machilida, Monura, Dasyleptidae, Dasyleptus, Triassomachilis, Mesozoic, Middle Triassic, Ladinian, Meride Limestone, Monte San Giorgio, Switzerland.
Dasyleptus triassicus n. sp. (Monura: Dasyleptidae) wird aus dem Ladinischen (Mitteltrias) Meride-Kalke von Monte San Giorgio in der Schweiz beschrieben. Es handelt sich um den ersten Fossilnachweis eines fl ügellosen Insektes in der Trias und um den ersten mesozoischen Nachweis der ausgestorbenen Gruppe Monura. Diese waren zuvor nur aus dem paläozoischen Oberkarbon und Unterperm bekannt. Die neue Entdeckung belegt, dass diese zarten Insekten das große Massenaussterbeereignis am Ende des Perm überlebt hatten. Dasyleptus wird als neote¬ner Felsenspringer angesehen, der am Spülsaum von Meeresküsten und am Ufer von Süßgewässern und Sümpfen lebte. Ein Schwestergruppenverhältnis von Dasyleptidae und Ectognatha wird als unzureichend begründet zurück¬gewiesen und die Monura als Unterordnung der Archaeognatha bestätigt, die in einem Schwestergruppenverhältnis zu allen rezenten Felsenspringern (Unterordnung Machilida n. stat.) stehen. Fossile Insekten mit ungewöhnlichen Merkmalen, die aus dem Karbon von Mazon Creek als ‘Dasyleptus’ spec. von KUKALOVÁ-PECK beschrieben wur¬den, werden hier als „Chimären“ aus drei unterschiedlichen Organismen erachtet: 1) echte Monuren; 2) Cercopo¬data; 3) Stammgruppenvertreter der Insekten, die nicht mit den Dasyleptidae verwandt sind, die aber vielleicht mit dem angeblichen fossilen Silberfi sch Ramsdelepidion kongenerisch sind. Ihr Status als authentische Fossilien wirdunterstützt und die Behauptung von „Überpräparation“ als unzureichend begründet zurückgewiesen.
The Triassic represents a critical period for understanding the turnover of insect fauna from the Paleozoic to the Mesozoic following the end-Permian mass extinctions (EPME); however, fossil deposits from the Early-Middle Triassic are scarce. The exceptionally preserved 239 million-year-old fossil insect fauna recorded at Monte San Giorgio (Switzerland), including 248 fossils representing 15 major insect clades is presented here. Besides the exceptional features, including their small size and excellent preservation, the fossils have importance in the evolutionary history of the group. The taxonomic and ecological diversity recovered, including both freshwater (dragonflies and caddisflies) and terrestrial taxa (true bugs and wasps), demonstrates that complex environments sustained a paleocommunity dominated by monurans (thought not to have survived the EPME), midges, and beetles. Interestingly, a blattodean-like fossil bearing an external ootheca was also found, important for understanding Paleozoic roachoids to extant cockroaches’ transition and the evolution of maternal brood care. Moreover, the youngest and first complete specimen of †Permithonidae and the oldest sawfly fossils were discovered. Finally, round-shaped bodies, compatible with seminal capsules or lycophyte spores, were found on the abdomens of several midge-like individuals. If these are spores, non-seed-bearing plants could have been the first entomophilous plants rather than gymnosperms, as recently supposed. Altogether, these fossils contribute substantially to understanding insect evolution and Paleozoic-Mesozoic faunal turnover.
We introduce probability plotting for general use in the analysis of biological and palaeontological morphometric data. When applied to morphometric data, this analytical tool can yield palaeoecological, ontogenetic and demographic information. We have adapted and expanded a statistical tool used in reliability engineering, mechanical or electrical lifetime analysis, geochemistry and ore mineral analysis to analyse fossil populations. The technique is explained stepwise in a ‘user's manual’ format. Its power is to characterize statistical distribution types, to determine whether these distributions are skewed or truncated, and to resolve and quantify the components of mixed distributions, which in palaeontological data potentially represent morphological groupings such as cohorts or sexual dimorphs. The ease of application and simplicity are surprising. A probability plot of growth series data (e.g. skull lengths, femoral lengths, snout‐to‐vent lengths or other morphometrics) typically shows complex non‐normal distribution of the data because of multimodal composition. We show that these component modes, which are generally, but not always normal (i.e. Gaussian), can be resolved, and that they correspond to yearly age groups (cohorts), sexual dimorphs, pre‐ and post‐metamorphic forms, other ontogenetic stages or possibly mixed taxa. When these component size distributions are associated with an age group or sex, several important palaeoecological calculations become possible. These include growth curves, age and sex distributions, sexual dimorphism indices, etc. We demonstrate the biological and palaeontological utility of probability plots with several examples including a Permian wingless insect, an extant unionid bivalve, a Triassic metoposaurid amphibian, an extant lizard, and a Triassic theropod dinosaur.
Among the incomparably diverse group of insects no cases of central nervous system (CNS)
preservation have been so far described in compression fossils. A third of the fossil insects collected
from a 240–239 million year old (Ma) level at Monte San Giorgio UNESCO World Heritage (Switzerland-
Italy) underwent phosphatization, resulting in the extraordinary preservation of soft tissues. Here we
describe Gigamachilis triassicus gen. et sp. nov. (Archaeognatha: Machiloidea: Machilidae) that, with
an estimated total length of ~80 millimeters, represents the largest apterygote insect ever recorded.
The holotype preserves: (i) components of the CNS represented by four abdominal ganglia, optic
lobes with neuropils and compound retina; (ii) muscular bundles. Moreover, G. triassicus, possessing
morphological features that prompt its assignment to the extant archaeognathan ingroup Machilidae,
places the origin of modern lineages to Middle Triassic. Interestingly, at Monte San Giorgio, in the same
stratigraphic unit the modern morphology of G. triassicus co-occurs with the ancient one represented
by Dasyleptus triassicus (Archaeognatha: †Monura). Comparing these two types of body organization
we provide a new reconstruction of the possible character evolution leading towards modern
archaeognathan forms, suggesting the acquisition of novel features in a lineage of apterygote insects
during the Permian or the Lower Triassic.
The following list provides citations for 363 scientific contributions, including 13 edited volumes and books, produced by Alexandr P. Rasnitsyn. Naturally, the list presented here is a static representation of Alex’s contributions and we look forward to years of his forthcoming publications to our shared science. Thus, this list only encompasses those papers published as of 1 August 2011. We have published it here so as to bring to the attention of colleagues Alex’s numerous and multifaceted accomplishments, and why he so richly deserves our admiration. In addition, we believe the following list is the most thorough and accurate accounting of his published scientific activities. Given that many of his works are in his native Russian, we believe this list will serve as a tool for directing interested individuals to English translations, where available.
