Late Devonian Period Research Articles

Preliminary investigation of the eruption time of kimberlite in the Late Devonian in Mengyin, Shandong

Kimberlite in the Mengyin area serves as an excellent medium for studying the characteristics and evolutionary processes of the Paleozoic mantle. In order to determine the age of the primary calcite within the kimberlite, in situ carbonate U–Pb dating was conducted in the Mengyin area. The results indicate that the primary calcite in the kimberlite originated approximately 383 ± 18 Ma (MSWD = 6.6). This age constraint suggests that the eruption of the kimberlite took place during this period, leading to the thermal alteration of limestone xenoliths, ultimately forming marble. Consequently, it can be inferred that lithospheric thinning occurred no later than the Late Devonian period. Fluid inclusions found within the marble provide further insights into its formation. The recorded formation temperature of the marble ranges from 243°C to 370°C, with a salinity range of 2.57%–14.77% (NaCl). The pressure estimates fall within the range of 3.22–20.70 MPa, indicating a depth mainly between 900 and 1,000 m. Based on these findings, it can be inferred that the overall denudation depth in the west Shandong area, since the Late Devonian, is estimated to be approximately 900–1,000 m. Furthermore, the overall crustal rise rate is estimated to be approximately 3 m/Ma.

A new elpistostegalian from the Late Devonian of the Canadian Arctic

A fundamental gap in the study of the origin of limbed vertebrates lies in understanding the morphological and functional diversity of their closest relatives. Whereas analyses of the elpistostegalians Panderichthys rhombolepis, Tiktaalik roseae and Elpistostege watsoni have revealed a sequence of changes in locomotor, feeding and respiratory structures during the transition1–9, an isolated bone, a putative humerus, has controversially hinted at a wider range in form and function than now recognized10–14. Here we report the discovery of a new elpistostegalian from the Late Devonian period of the Canadian Arctic that shows surprising disparity in the group. The specimen includes partial upper and lower jaws, pharyngeal elements, a pectoral fin and scalation. This new genus is phylogenetically proximate to T. roseae and E. watsoni but evinces notable differences from both taxa and, indeed, other described tetrapodomorphs. Lacking processes, joint orientations and muscle scars indicative of appendage-based support on a hard substrate13, its pectoral fin shows specializations for swimming that are unlike those known from other sarcopterygians. This unexpected morphological and functional diversity represents a previously hidden ecological expansion, a secondary return to open water, near the origin of limbed vertebrates.

Geological structure and oil and gas potential of Domanik deposits in the central part of the Volga-Ural oil and gas basin

The paper describes the structure and depositional conditions of a domanicoid high-carbon formation (HCF) in the central part of the Volga-Ural oil and gas basin. The structure of the HCF depends on the structural relatedness and paleogeographic conditions of the Late Devonian period, where the time of maximum sea level standing within the basin led to deposition of high organic carbon content intervals. The structural-facies zonation of the HCF distribution area is associated with the zone of relatively deep-water depressions, the zone of slopes, highs and the shallow water shelf with numerous bioherm buildups. The boundaries of the zones were determined by the position of large structural elements of the Tatar and Bashkir arches and depressions of the Kama-Kinel system of troughs. These zones differ not only in the distribution of the thickness of HCF deposits, but also in the nature of the distribution of intervals of the section enriched in organic matter. The maximum number of interlayers enriched by organic matter of the siliceous-carbonate rocks is observed in the section of the Frasnian and Famennian deposits within the central part of the Kama-Kinel system of troughs. Numerous of oil shows from the HCF intervals indicate the potential for further study and spotting of promising areas for hard-to-recover hydrocarbon reserves exploration.

High-Resolution Late Devonian Magnetostratigraphy From the Canning Basin, Western Australia: A Re-Evaluation

Late Devonian time was a period of rapid upheaval in the Earth system, including climate change, sea level changes, widespread ocean anoxia, and the Frasnian-Famennian mass extinction; the cause(s) of these changes remain(s) uncertain. The Lennard Shelf of the Canning Basin in Western Australia contains carbonate reef sections spanning much of the Late Devonian Epoch and has been sampled for paleomagnetic analysis with studies by Hansma and colleagues in 2015 and Playton and colleagues in 2016. However, previous paleomagnetic directions were scattered and their use for magnetostratigraphy has been questioned. Here, rock magnetic data and magnetostratigraphy for a late Devonian drill-core from the Lennard Shelf were analyzed. Three magnetostratigraphic interpretations were made using different paleopoles that showed good correlation with each other and the earlier interpretations by Playton and colleagues in 2016. Additionally, the rock magnetic data revealed the samples contain various mixtures of detrital and diagenetic minerals, the former of which should be viable recorders of primary magnetic signatures. Even in samples with these detrital phases, paleomagnetic data were often noisy and produced ambiguous polarity assignments, likely due to the anomalously weak Devonian field. Because of this ambiguity and the absence of a robust paleopole, broader correlations for this critical time-period will be difficult without additional paleomagnetic data from the late Devonian Period. Expanded data for this interval could eventually shed light on the timing, causes, and rates of the Frasnian-Famennian mass extinction and other environmental shifts in the late Devonian Epoch.

Morphometric variance, evolutionary constraints and their change through time in Late Devonian Palmatolepis conodonts.

Phenotypic variation is the raw material of evolution. Standing variation can facilitate response to selection along "lines of least evolutionary resistance", but selection itself might alter the structure of the variance. Shape was quantified using 2D geometric morphometrics in Palmatolepis conodonts through the Late Devonian period. Patterns of variance were characterized along the record by the variance-covariance matrix (P-matrix) and its first axis (Pmax). The Late Frasnian was marked by environmental oscillations culminating with the Frasnian/Famennian mass extinction. A shape response was associated with these fluctuations, together with a deflection of the Pmax and the P-matrix. Thereafter, along the Famennian, Palmatolepis mean shape shifted from broad elements with a large platform to slender elements devoid of platform. This shift in shape was associated with a reorientation of Pmax and the P-matrix, due to profound changes in the functioning of the elements selecting for new types of variants. Both cases provide empirical evidences that moving adaptive optimum can reorient phenotypic variation, boosting response to environmental changes. On such time scales, the question seems thus not to be whether the P-matrix is stable, but how it is varying in response to changes in selection regimes and shifts in adaptive optimum.

Astronomical time calibration of the Upper Devonian Lali section, South China

Abstract The Late Devonian Period was a critical geological interval, affected by numerous significant global bio- and environmental events, including the Kellwasser, annulata and Hangenberg events, and a major climate transition leading to the Carboniferous ice ages. The timing and pattern of these events are unclear due to lack of the precise time scale. In this study, an analysis of calcium concentration series was carried out on the Upper Devonian cyclostratigraphic slope-facies of the Lali section, South China. Objective testing of the section indicates the presence of astronomical forcing: long orbital eccentricity, short eccentricity, obliquity, and precession index. Two independent astrochronologies were developed for the Ca series and compared with spectral analysis. The age of the Devonian–Carboniferous boundary (358.9 ± 0.4 Ma) was selected as an “anchor”, and an Astronomical Time Scale (ATS) was constructed from the late Frasnian to early Tournaisian based on 405-kyr cycles. The ATS indicates a duration of the Famennian Stage of 14.4 ± 0.28 myr, and assigns 373.3 ± 0.49 Ma to the Frasnian–Famennian boundary. The durations of the Famennian conodont zones are also indicated. The timing of Famennian bio- and environmental events also can be established by the ATS. The Upper Kellwasser horizon starts at 373.4 Ma and is constrained to a duration of 100-kyr; a sharp positive carbon isotope excursion CIE, +3‰ recognized across the Frasnian–Famennian boundary lasts 300 kyr. The Lower and Upper annulata events each last 50-kyr with positive CIEs; and the ages of two CIE peaks are 361.7 Ma and 361.3 Ma, respectively. Five transgressive events, including the Nehden, Enkeberg, Dasberg, Strunian, and Hangenberg transgressions occur at 370.6 Ma, 368 Ma, 360.4 Ma, 360.1 Ma, and 358.9 Ma, respectively. Five regressive events i.e., the linguiformis, prima, Condroz, velifer, and Derwer regressions occur at 373.4 Ma, 371 Ma, 369 Ma, 362.3 Ma, and 359.2 Ma, respectively.

Elpistostege and the origin of the vertebrate hand.

The evolution of fishes to tetrapods (four-limbed vertebrates) was one of the most important transformations in vertebrate evolution. Hypotheses of tetrapod origins rely heavily on the anatomy of a few tetrapod-like fish fossils from the Middle and Late Devonian period (393-359million years ago)1. These taxa-known as elpistostegalians-include Panderichthys2, Elpistostege3,4 and Tiktaalik1,5, none of which has yet revealed the complete skeletal anatomy of the pectoral fin. Here we report a 1.57-metre-long articulated specimen of Elpistostege watsoni from the Upper Devonian period of Canada, which represents-to our knowledge-the most complete elpistostegalian yet found. High-energy computed tomography reveals that the skeleton of the pectoral fin has four proximodistal rows of radials (two of which include branched carpals) as well as two distal rows that are organized as digits and putative digits. Despite this skeletal pattern (which represents the most tetrapod-like arrangement of bones found in a pectoral fin to date), the fin retains lepidotrichia (fin rays) distal to the radials. We suggest that the vertebrate hand arose primarily from a skeletal pattern buried within the fairly typical aquatic pectoral fin of elpistostegalians. Elpistostege is potentially the sister taxon of all other tetrapods, and its appendages further blur the line between fish and land vertebrates.

Mudskippers in the Mekong Delta might tell us something about vertebrate transition to land?

Rise of vertebrates from water to land, which seems to be occurred in the mid to late Devonian Period (about 390 to 360 million years ago), shows one of the most crucial events throughout the existence of life [1]. There are many longstanding debates about emergence of vertebrates in the Paleozoic from marine environment or freshwater environments [2-6]. Through our four-year survey in the field in the place called Mekong Delta which is situated in Vietnam, we explored mudskippers a special species, Periophthalmodon septemradiatus, which inhabits the littoral zones in brackish waters near the coast of fully freshwater areas 150 km from the river mouth along the Mekong River [7]. Mudskippers which are amphibious gobies which usually inhabits intertidal mudflats from estuaries, subtropical coasts and tropical coasts and shows behavioral, physiological and morphological adaptations of life on land [8]. The most terrestrial fishes named Periophthalmodon septemradiatus are living today. During the period of our field survey, we have not seen any P. septemradiatus ventures into water. The substantial portal of gut content of this fish is constituted by ants, further supporting the high terrestriality of the fish

Anthraxolite Evolution and Vanadium Enrichment Mechanism in the Tanjianshan Group, Upper Ordovician in the Northern Qaidam Basin

Earlier researchers have examined the interaction between organic matter (OM) and metals, but the paragenesis of anthraxolite and mechanism enrichment of vanadium (V) need further study. Our recent geological field survey discovered that anthraxolite contains a substantial amount of V in the Member “a” of the Tanjianshan Group, Upper Ordovician in the northern margin of the Qaidam Basin. Different organic geochemical studies (fluid inclusions, zircon U–Pb dating, and petrochemistry) were conducted to examine the origin and evolution of anthraxolite, as well as the enrichment of V. The extractable organic matter (EOM) content of anthraxolite is low, while it contains a high amount of non-hydrocarbon and asphaltene. Anthraxolite is over-mature with its equivalent vitrinite reflectance being up to 4.9%. Anthraxolite is sourced from mudstone of Member “a” of the Tanjianshan Group. There were two hydrocarbon charging phases: (i) Late Devonian; and (ii) Carboniferous. Multiple magmatic thermal events took place after the Late Devonian period, resulting in hydrocarbon fluid cracking, metamorphism, and finally the formation of anthraxolite. Marine hot water deposition was irrelevant to enrichment of V. It is inferred that V originated during biological and biochemical processes, then migrated and accumulated with hydrocarbon formation and evolution, and finally enriched in anthraxolite.

Prototaxites - zagadkowe organizmy kopalne

Prototaxites to wymarły rodzaj organizmów żywych; występowały one na całym świecie od późnego syluru do późnego dewonu (420-370 mln lat temu). Wymarły jednocześnie z rozwojem roślin krzewiastych i drzewiastych. Miały cylindryczną, wzniesioną formę, przypominającą kolumnę o wymiarach nawet 8 m wysokości i 1 m szerokości, z pojedynczymi, krótkimi rozgałęzieniami w szczytowej części. W ciągu wieków kwestia interpretacji ich skamieniałości była przedmiotem ożywionej debaty naukowej. Obecnie uważa się, że najprawdopodobniej były organizmami symbiotycznymi, związkiem grzyba i glonu.

Unique growth strategy in the Earth’s first trees revealed in silicified fossil trunks from China

Cladoxylopsida included the earliest large trees that formed critical components of globally transformative pioneering forest ecosystems in the Mid- and early Late Devonian (ca. 393-372 Ma). Well-known cladoxylopsid fossils include the up to ∼1-m-diameter sandstone casts known as Eospermatopteris from Middle Devonian strata of New York State. Cladoxylopsid trunk structure comprised a more-or-less distinct cylinder of numerous separate cauline xylem strands connected internally with a network of medullary xylem strands and, near the base, externally with downward-growing roots, all embedded within parenchyma. However, the means by which this complex vascular system was able to grow to a large diameter is unknown. We demonstrate-based on exceptional, up to ∼70-cm-diameter silicified fossil trunks with extensive preservation of cellular anatomy from the early Late Devonian (Frasnian, ca. 374 Ma) of Xinjiang, China-that trunk expansion is associated with a cylindrical zone of diffuse secondary growth within ground and cortical parenchyma and with production of a large amount of wood containing both rays and growth increments concentrically around individual xylem strands by normal cambia. The xylem system accommodates expansion by tearing of individual strand interconnections during secondary development. This mode of growth seems indeterminate, capable of producing trees of large size and, despite some unique features, invites comparison with secondary development in some living monocots. Understanding the structure and growth of cladoxylopsids informs analysis of canopy competition within early forests with the potential to drive global processes.

Combining shock barometry with numerical modeling: Insights into complex crater formation—The example of the Siljan impact structure (Sweden)

AbstractSiljan, central Sweden, is the largest known impact structure in Europe. It was formed at about 380 Ma, in the late Devonian period. The structure has been heavily eroded to a level originally located underneath the crater floor, and to date, important questions about the original size and morphology of Siljan remain unanswered. Here we present the results of a shock barometry study of quartz‐bearing surface and drill core samples combined with numerical modeling using iSALE. The investigated 13 bedrock granitoid samples show that the recorded shock pressure decreases with increasing depth from 15 to 20 GPa near the (present) surface, to 10–15 GPa at 600 m depth. A best‐fit model that is consistent with observational constraints relating to the present size of the structure, the location of the downfaulted sediments, and the observed surface and vertical shock barometry profiles is presented. The best‐fit model results in a final crater (rim‐to‐rim) diameter of ~65 km. According to our simulations, the original Siljan impact structure would have been a peak‐ring crater. Siljan was formed in a mixed target of Paleozoic sedimentary rocks overlaying crystalline basement. Our modeling suggests that, at the time of impact, the sedimentary sequence was approximately 3 km thick. Since then, there has been around 4 km of erosion of the structure.

A Devonian tetrapod-like fish reveals substantial parallelism in stem tetrapod evolution.

The fossils assigned to the tetrapod stem group document the evolution of terrestrial vertebrates from lobe-finned fishes. During the past 18 years the phylogenetic structure of this stem group has remained remarkably stable, even when accommodating new discoveries such as the earliest known stem tetrapod Tungsenia and the elpistostegid (fish-tetrapod intermediate) Tiktaalik. Here we present a large lobe-finned fish from the Late Devonian period of China that disrupts this stability. It combines characteristics of rhizodont fishes (supposedly a basal branch in the stem group, distant from tetrapods) with derived elpistostegid-like and tetrapod-like characters. This mélange of characters may reflect either detailed convergence between rhizodonts and elpistostegids plus tetrapods, under a phylogenetic scenario deduced from Bayesian inference analysis, or a previously unrecognized close relationship between these groups, as supported by maximum parsimony analysis. In either case, the overall result reveals a substantial increase in homoplasy in the tetrapod stem group. It also suggests that ecological diversity and biogeographical provinciality in the tetrapod stem group have been underestimated.

Evolution processes of Ordovician–Devonian arc system in the South‐Kitakami Massif and its relevance to the Ordovician ophiolite pulse

AbstractThe South Kitakami Massif is one of the oldest geological domains in Japan having Silurian strata with acidic pyroclastic rocks and Ordovician–Silurian granodiorite–tonalite basement, suggesting that it was matured enough to develop acidic volcanisms in the Silurian period. On the northern and western margin of the South Kitakami Massif, an Ordovician arc ophiolite (Hayachine–Miyamori Ophiolite) and high‐pressure and low‐temperature metamorphic rocks (Motai metamorphic rocks) exhumed sometime in the Ordovician–Devonian periods are distributed. Chronological, geological, and petrochemical studies on the Hayachine–Miyamori Ophiolite, Motai metamorphic rocks, and other early Paleozoic geological units of the South Kitakami Massif are reviewed for reconstruction of the South Kitakami arc system during Ordovician to Devonian times with supplementary new data. The reconstruction suggests a change in the convergence polarity from eastward‐ to westward‐dipping subduction sometime before the Late Devonian period. The Hayachine–Miyamori Ophiolite was developed above the eastward‐dipping subduction through three distinctive stages. Two separate stages of overriding plate extension inducing decompressional melting with minor involvement of slab‐derived fluid occurred before and after a stage of melting under strong influence of slab‐derived fluids. The first overriding plate extension took place in the back‐arc side forming a back‐arc basin. The second one took place immediately before the ophiolite exhumation and near the fore‐arc region. We postulate that the second decompressional melting was triggered by slab breakoff, which was preceded by slab rollback inducing trench‐parallel wedge mantle flow and non‐steady fluid and heat transport leaving exceptionally hydrous residual mantle. The formation history of the Hayachine–Miyamori Ophiolite implies that weaker plate coupling may provide preferential conditions for exhumation of very hydrous mantle. Very hydrous peridotites involved in arc magmatism have not yet been discovered except for in the Cambrian–Ordovician periods, suggesting its implications for global geodynamics, such as the thermal state and water circulation in the mantle.

The Yubileinoe porphyry Cu-Au deposit (South Urals, Russia): SHRIMP-II U-Pb zircon age and geochemical features of ore-bearing granitoids

The economic Yubileinoe porphyry Cu–Au deposit is located in the southernmost part of the femic Tagil–Magnitogorsk–Western Mugodzhary volcanogenic megazone (near Emba, South Urals). Only a few small porphyry Cu–Au deposits (Med� nogorskoe and, probably, the Miass group of deposits) are known further north. The megazone proper hosts Middle Devonian deposits (Salavatskoe, large Gume� shevskoe) and many ore occurrences of the porphyry (Au)–Cu type [2, 3, 9, 11]. There is also the large Verkhneural’skoe porphyry Cu–Mo ore occurrence ( ). To date, the age of the Yubileinoe deposits has remained unknown, which hampered interpreta� tion of its position in the metallogenic structure of the region. The new data obtained during this study dem� onstrate that the last deposit differs notably from other porphyry ore deposits of the megazone in its ore spe� cialization, geochemical properties, and age. The Middle–Late Devonian period characterized by the island arc regime was probably characterized by the repeated formation of porphyry deposits. The Yubileinoe deposits are confined to the synon� ymous tubular porphyry stock 300 × 210 m in size with granitoids largely represented by biotite–amphibole plagioadamelite porphyries, which were probably intruded during two phases [3, 4]. These rocks contain locally up to 2–10% of K feldspar. The granitoids are always slightly or moderately sericitized and chlori� tized. The phenocrysts are represented by the follow� ing minerals (%): plagioclase (25–35), quartz (8–15), and biotite and amphibole (5–8). The average con� tents of the main chemical components are as follows (%): SiO2, 69.4 (ranging from 67 to 71); TiO 2, 0.29; Al2O3, 15.1; (FeO + 0.9Fe2O3), 2.0; MgO, 1.3; CaO, 2.3; N2O, 4.5; K2O, 1.8 (ranging from 0.3 to 2.5). The

Phanerozoic Paleomagnetism Characteristics of the Qomolangma Area in Tibet

Abstract:This paper conducts systematic test research on the 2920 paleomagnetic directional samples taken from Ordovician‐Paleogene sedimentary formation in the north slope of Qomolangma in south of Tibet and obtains the primary remanent magnetization component and counts the new data of paleomagnetism the times. Based on the characteristic remanent magnetization component, it calculates the geomagnetic pole position and latitude value of Himalaya block in Ordovician‐Paleogene. According to the new data of paleomagnetism, it draws the palaeomagnetic polar wander curve and palaeolatitude change curve of the north slope of Qomolangma in Ordovician‐Paleogene. It also makes a preliminary discussion to the structure evolution history and relative movement of Himalaya bloc. The research results show that many clockwise rotation movements had occurred to the Himalaya block in northern slope of Qomolangmain the process of northward drifting in the phanerozoic eon. In Ordovician‐late Cretaceous, there the movement of about 20.0° clockwise rotation occurred in the process of northward drifting. However, 0.4° counterclockwise rotation occurred from the end of late Devonian epoch to the beginning of early carboniferous epoch; 6.0° and 8.0° counterclockwise rotation occurred in carboniferous period and early Triassic epoch respectively, which might be related with the tension crack of continental rift valley from late Devonian period to the beginning of early carboniferous epoch, carboniferous period and early Triassic epoch. From the Eocene epoch to Pliocene epoch, the Himalaya block generated about 28.0° clockwise while drifting northward with a relatively rapid speed. This was the result that since the Eocene epoch, due to the continuous expansion of mid‐ocean ridge of the India Ocean, the neo‐Tethys with the Yarlung Zangbo River as the main ocean basin closed to form orogenic movement and the strong continent‐continent collision orogenic movement of the east and west Himalayas generated clockwise movement in the mid‐ Himalaya area. According to the calculation of palaeolatitude data, the Himalaya continent‐continent collusion orogenic movement since the Eocene epoch caused the crustal structure in Indian Plate‐ Himalaya folded structural belt‐ Lhasa block to shorten by at least 1000 km. The systematic research on the paleomagnetism of Qomolangma area in the phanerozoic eon provides a scientific basis to further research the evolution of Gondwanaland, formation and extinction history of paleo‐Tethys Ocean and uplift mechanism of the Qinghai‐Tibet Plateau.

A complete insect from the Late Devonian period

After terrestrialization, the diversification of arthropods and vertebrates is thought to have occurred in two distinct phases, the first between the Silurian and the Frasnian stages (Late Devonian period) (425-385 million years (Myr) ago), and the second characterized by the emergence of numerous new major taxa, during the Late Carboniferous period (after 345 Myr ago). These two diversification periods bracket the depauperate vertebrate Romer's gap (360-345 Myr ago) and arthropod gap (385-325 Myr ago), which could be due to preservational artefact. Although a recent molecular dating has given an age of 390 Myr for the Holometabola, the record of hexapods during the Early-Middle Devonian (411.5-391 Myr ago, Pragian to Givetian stages) is exceptionally sparse and based on fragmentary remains, which hinders the timing of this diversification. Indeed, although Devonian Archaeognatha are problematic, the Pragian of Scotland has given some Collembola and the incomplete insect Rhyniognatha, with its diagnostic dicondylic, metapterygotan mandibles. The oldest, definitively winged insects are from the Serpukhovian stage (latest Early Carboniferous period). Here we report the first complete Late Devonian insect, which was probably a terrestrial species. Its 'orthopteroid' mandibles are of an omnivorous type, clearly not modified for a solely carnivorous diet. This discovery narrows the 45-Myr gap in the fossil record of Hexapoda, and demonstrates further a first Devonian phase of diversification for the Hexapoda, as in vertebrates, and suggests that the Pterygota diversified before and during Romer's gap.

Dispatches

Dispatches

Tetrapod trackways from the early Middle Devonian period of Poland

The fossil record of the earliest tetrapods (vertebrates with limbs rather than paired fins) consists of body fossils and trackways. The earliest body fossils of tetrapods date to the Late Devonian period (late Frasnian stage) and are preceded by transitional elpistostegids such as Panderichthys and Tiktaalik that still have paired fins. Claims of tetrapod trackways predating these body fossils have remained controversial with regard to both age and the identity of the track makers. Here we present well-preserved and securely dated tetrapod tracks from Polish marine tidal flat sediments of early Middle Devonian (Eifelian stage) age that are approximately 18 million years older than the earliest tetrapod body fossils and 10 million years earlier than the oldest elpistostegids. They force a radical reassessment of the timing, ecology and environmental setting of the fish-tetrapod transition, as well as the completeness of the body fossil record.

Suppression of neuronal excitability by the secretion of the lamprey (Lampetra japonica) provides a mechanism for its evolutionary stability

Lampreys are one of the most primitive vertebrates still living today. They attach themselves to the body surface of the host fish through their sucker-like mouths and suck blood of the host for days. Recent fossil evidence has indicated that morphology of lampreys in the late Devonian period, over 360 million years ago, already possessed the present day major characteristics, suggesting the evolutionary stability of a highly specialized parasitic feeding habit. Obviously, nociceptive responses and hemostasis of the host are two major barriers to long-term feeding of the parasitic lamprey. It has been found, to counteract hemostasis of the host, that paired buccal glands of lampreys secrete antihemostatic compounds to prevent blood of the host from coagulation. However, it is not known how lampreys make the host lose nociceptive responses. Here, we prepared components of the crude extract from the buccal glands of the lampreys (Lampetra japonica). Then, we show that crude extract and one of its purified components reduce the firing frequency of neuronal action potentials probably through inhibiting the voltage-dependent Na(+) channels. As the voltage-gated Na(+) channels are highly conserved throughout evolution, we argue that the secretion of the lampreys could exert the similar effect on the Na(+) channels of their host fish as well. Therefore, together with its antihemostatic effect, the secretion due to its inhibitory effect on neuronal excitability might provide a mechanism for the parasitic lampreys to keep their evolutionary stability.