Mysore Plateau Research Articles

Three new cryptic species of South Asian Cnemaspis Strauch, 1887 (Squamata, Gekkonidae) from Karnataka, India

We describe three new small-bodied, cryptic species of south AsianCnemaspisbelonging to themysoriensisandgoaensisclades from the Mysore Plateau and the Western Ghats biodiversity hotspot in Karnataka, peninsular India; and provide a key to members of each clade, besides providing the first ND2 sequence data forC. ranganaensis.Cnemaspis tigrissp. nov.from Kaiwara in Karnataka is a member of themysoriensisclade and can be morphologically distinguished from all six described members of the clade in a number of meristic characters and subtle differences in colouration, beside ≥ 12.1–23.4 % uncorrected pairwise ND2 sequence divergence.Cnemaspis sakleshpurensissp. nov.from Sakleshpur andC. vijayaesp. nov.from Coorg, both in the Western Ghats of Karnataka, are members of thegoaensisclade and are easily diagnosed from all three described members of the clade in meristic characters beside 5.2–14.8 % divergence from described members of the clade and 14.6 % from each other in uncorrected pairwise ND2 sequence divergence. The discovery of these new species from two different clades and biogeographic regions is not surprising, given the steep rise in the number of species ofCnemaspisknown from peninsular India. Comprehensive geographic sampling in conjunction with molecular and morphological data is essential to understand the true diversity and distributional ranges of species within this ancient clade of gekkonid lizards.

A new medium-sized rupicolous Cnemaspis Strauch, 1887 (Squamata: Gekkonidae) of the C. bangara clade from granite boulder habitats in Krishnagiri, Tamil Nadu, India.

We describe a new species of the Cnemaspis bangara clade from a rocky hillock near Kugai Periya Mariamman Temple, Krishnagiri fort, Krishnagiri District of Tamil Nadu, India. Cnemaspis krishnagiriensis sp. nov. can be diagnosed from all other peninsular Indian congeners by its medium body size (maximum SVL 40 mm), heterogeneous dorsal pholidosis, spine-like tubercles absent on flanks; presence of four femoral pores on each thigh separated on either side by nine or 10 poreless scales from three continuous precloacal pores in males; tail with enlarged, strongly keeled, conical tubercles forming four whorls on anterior portion, six tubercles in first whorl, four tubercles in second to fourth whorls, enlarged tubercles restricted to only paravertebral region on rest of the tail; median row of sub-caudals smooth and distinctly enlarged, and a unique colour pattern. The new species can be diagnosed from members of C. bangara clade by the number of dorsal tubercles rows at mid-body, the number of enlarged tubercles in paravertebral rows, the number of ventral scales across belly at mid-body, the number longitudinal ventral scales from mental to cloaca, the number of femoral and precloacal pores and poreless scales separating these series, and subtle colour pattern differences; besides 9.217.6 % uncorrected ND2 sequence divergence. Cnemaspis krishnagiriensis sp. nov. is the fourth member of the recently described bangara clade and is the first that is known to be distributed <900 m asl.. The discovery of yet another endemic species of Cnemaspis from lower elevations of the Mysore Plateau once again highlights the need of dedicated systematic sampling to uncover the true diversity of Cnemaspis. We also address a nomenclatural issue related to the recently described Cnemaspis stellapulvis Khandekar, Thackeray Agarwal.

On the taxonomy and systematics of the recently described Lycodon deccanensis Ganesh, Deuti, Punith, Achyuthan, Mallik, Adhikari, Vogel, 2020 (Serpentes, Colubridae) from India

Lycodon deccanensisGanesh, Deuti, Punith, Achyuthan, Mallik, Adhikari, Vogel, 2020 was recently described from the Mysore plateau of Karnataka based solely on morphology but lacking in-depth descriptions and comparisons. A scrutiny of the description reveals that the type series, of two specimens, comprise specimens of two different species along with discrepancies throughout the paper. Surveys conducted near the type locality of the species led to the discovery of additional specimens, which allow us to provide an elaborate description of the species and present data on its phylogenetic relationship with members of the genus and comments on the systematics ofLycodonof India. Results from molecular phylogenetics suggest thatLycodon deccanensisis a member of theL. aulicusclade based on molecular data for mitochondrial cytochrome b gene and shows an un-corrected p-distance (sequence divergence) of 14–17% from other members of theLycodon aulicusclade.

A new cryptic Cnemaspis Strauch (Squamata: Gekkonidae) from an isolated granite hill on the Mysore Plateau, Karnataka, India

We describe a cryptic new species of the Cnemaspis mysoriensis complex from an isolated rocky hillock near Yadiyur, Mandya District of south Karnataka, India. Cnemaspis stellapulvis sp. nov. can be diagnosed from all other peninsular Indian congeners by its small body size (SVL <32 mm), presence of spine-like tubercles on the flanks, heterogeneous dorsal pholidosis, two or three femoral pores on each thigh separated on either side by eight poreless scales from a continuous series of two precloacal pores in males, tail with enlarged, strongly keeled, conical tubercles forming whorls, median row of sub-caudals smooth and slightly enlarged, and a distinct colour pattern. The new species can be diagnosed from members of C. mysoriensis clade by the number of femoral and precloacal pores and number of poreless scales separating these series, the number of dorsal tubercles rows at mid-body, the number of ventral scales across the belly at mid-body and subtle colour pattern differences; besides 13.4-21.4 % uncorrected ND2 sequence divergence. In this paper, we define the Cnemaspis mysoriensis clade and provide a diagnosis and comparison against peninsular Indian congeners. We also provide major diagnostic characters for members of the C. mysoriensis clade. The discovery of yet another endemic species of Cnemaspis from one of the many isolated granite rocky hills on Mysore Plateau highlights the possibilities of presence of many more cryptic undescribed species.

Granite boulders act as deep‐time climate refugia: A Miocene divergent clade of rupicolous Cnemaspis Strauch, 1887 (Squamata: Gekkonidae) from the Mysore Plateau, India, with descriptions of three new species

We describe a divergent clade and three new rupicolous species of dwarf geckos of the genus Cnemaspis from the Mysore Plateau, southern India. Cnemaspis bangarasp. nov., C. graniticola sp. nov., and C.yelagiriensis sp. nov. differ from each other by 9%–18% uncorrected ND2 sequence divergence and other South Asian Cnemaspis by 17%–33% and are morphologically distinguishable from all regional congeners and each other. The new species are known from only granite boulders in montane habitats (>1,000 m asl.), just 60–120 km straight-line distance apart from each other. A fossil-calibrated timetree and ancestral area reconstructions indicate South Asian Cnemaspis originated in Western Ghats forests with initial divergence in the Paleocene-Eocene making it perhaps the oldest Indian squamate clade. Cnemaspis that occur in Peninsular India in the dry zone outside the Western Ghats form three independently derived clades that occur in significantly warmer and drier habitats than those in the Western Ghats. The discovery of a Miocene divergent clade from rocky hills on the southern edge of the Mysore Plateau reveals these habitats as novel, long-term climate refugia. This adds to the body of work revealing ancient origins of taxa in the Indian dry zone and supports the Mysore Plateau as an important and overlooked hot spot of lizard biodiversity.

Sub-watershed Prioritization Based on Drainage Morphometric Analysis: A Case Study of Cauvery River Basin in South India

Abstract Prioritization of sub-watersheds in a river basin using morphometric parameters is one of the simplest approaches for development of watersheds for its use and management. In this perspective, a study has been undertaken in the Cauvery river basin in South India, using morphometric analysis of the entire river basin in relation to its 17 sixth order sub-watersheds. In this study, automated extraction of drainage network method was applied using geospatial techniques. Drainage morphometric analysis was performed through linear, aerial and relief aspects. Strahler stream order classification was applied for classifying the stream order. In general, dendritic and sub-dendritic types of drainage patterns are noticed in the Cauvery river basin. The total length of the river and basin area are 800 km and 82283 km2, respectively. Hypsometric analysis reveals that about 30% of the study area is covered by steep slope with deeply dissected landscapes and the remaining 70% spreads essentially in the Mysore plateau and Tamil Nadu plains which are generally having gentle slopes with an equilibrium stage of landscape development. Prioritization of sub-watershed was carried out based on compound parameter analysis by adding the values of linear and shape parameters of each sub-watershed. The results of prioritization of sub-watersheds reveal that about 88% of sub-watersheds that spread in the river basin fall under high and moderate priority categories for water resource developments. Only two subwatersheds fall under the low priority category which in turn are safe in the case of water resource development. The study warrants the need for more focused investigations and corrective measures including construction of appropriate recharge structures for improving the water potential of the river basin.

Two new Cnemaspis Strauch, 1887 (Squamata: Gekkonidae) from the Shevaroy massif, Tamil Nadu, India, with a preliminary ND2 phylogeny of Indian Cnemaspis

We present a preliminary ND2 phylogeny of South Asian Cnemaspis, recovering a number of deeply divergent clades within Indian Cnemaspis, endemic to the southern and northern Western Ghats besides the Mysore Plateau and hills of Tamil Nadu. There are a number of unnamed lineages that are >5% divergent on ND2 across the phylogeny, including three from the gracilis clade on an elevation gradient (800-1400 m asl.) around Yercaud in the Shevaroy massif, Salem district, Tamil Nadu. We describe two of these as new species- Cnemaspis shevaroyensis sp. nov. and Cnemaspis thackerayi sp. nov. are both allied to Cnemaspis gracilis and can be diagnosed from all other Indian Cnemaspis by the absence of spine-like scales on flank, heterogeneous dorsal pholidosis, presence of femoral and precloacal pores, tail with enlarged, strongly keeled, conical tubercles forming whorls, a median row of enlarged and smooth sub-caudals. They differ from C. gracilis and each other in body size, the number of tubercles around midbody, the number of tubercles in paravertebral rows, the number of femoral and precloacal pores, the number of poreless scales in-between precloacal pores and between femoral and precloacal pores, and subtle colour pattern differences; besides uncorrected mitochondrial sequence divergence (7.9-16.6 %). We also provide a description of Cnemaspis yercaudensis from its type locality and an additional locality. The discovery of two endemic species and a third unnamed divergent lineage from an isolated massif in peninsular India outside the Western Ghats indicate that many other such understudied hill ranges may harbour high endemic biodiversity.

Two new species of ground-dwelling Cyrtodactylus (Geckoella) from the Mysore Plateau, south India.

Two new species of ground-dwelling geckos of the genus Cyrtodactylus (Geckoella) are described from the Mysore Plateau, in southern India. The new species are members of the C. collegalensis species complex, with 8.7 % uncorrected ND2 sequence divergence from each other and greater than 10 % divergence from described members of the C. collegalensis complex, from which they differ in subtle aspects of colour pattern and morphometric ratios. The type localities of the new species are ~ 130 km apart, and 100 km and 225 km from the type locality of C. collegalensis in the Biligiriranga Hills. The discovery of these new species in isolated mountains within a small area suggests other high elevation areas in the region may have undescribed species, and a redefinition of biodiversity patterns in peninsular India.

New species of geckos discovered in Mysore Plateau

New species of geckos discovered in Mysore Plateau

Historical Note: Old Water-Works on the Eastern Part of Mysore Plateau

Historical Note: Old Water-Works on the Eastern Part of Mysore Plateau

First 40Ar/39Ar dating of intense Late Palaeogene lateritic weathering in Peninsular India

Lateritic surface processes have shaped large platform and cratons of the tropical belt. Constraining the timing of such processes is crucial to decipher their role in cratonic morphogenesis and their response to long-term climatic change and lithospheric deformation. Weathering histories have been documented for South America, Africa and Australia, but precise time constraints of the lateritic weathering processes in South India are still lacking. We present 40Ar/39Ar ages of supergene cryptomelane (K–Mn oxide) formed in the Sandur Mn ore deposits exposed on the highest lateritic paleolandsurface that once covered the Mysore plateau and the adjacent Deccan Traps. Significant 40Ar/39Ar ages are estimated between ∼36 and ∼26 Ma from well-defined plateaus in step heating 39Ar release spectra and from best-fitted inverse isochrones. These ages constitute firm time constraints that document intense late Eocene–Oligocene lateritic weathering over Peninsular India under the influence of warm and wet climate comparable to that prevailing in tropical humid forests. These results imply that Southern India was weathered between ∼36 and 26 Ma and may have been dissected mostly in the Neogene.

Petrography and geochemical characteristics of the sediments of the small River Hemavati, Southern India: Implications for provenance and weathering processes

Small rivers (≤ 100 km length) are likely to drain fewer rock types. Therefore, their solutes and sediments are good indicators of weathering environments typical of their basins and help constraining the nature of their source rocks. To understand this, the texture, mineralogy, major and trace element compositions of the sediments deposited by the River Hemavati, a northern upland tributary of the Cauvery River in southern India, are analyzed and discussed. The Hemavati sediments are overall of fine sand size (mean 2–3ϕ), and have high concentrations of FeO (≤ 7 wt.%), TiO 2 (≤ 1.2 wt.%), Cr (≤ 350 ppm) and Ni (≤ 125 ppm). Major and trace element distribution call for a binary source for the sediments, and particularly point to contrasting climatic conditions of their provenances. The source areas in the upstream and downstream parts are exposed to sub-humid high relief and sub-arid low relief conditions, respectively, with distinct weathering characteristics. The CIA values (85–48) decrease from near the source to downstream, suggesting that the downstream rain-shadow part of the catchment suffered only minor chemical weathering. On the other hand, the REE distribution in the Hemavati sediments indicates contrasting lithologies in their provenance, and is not controlled by chemical weathering. On the basis of REE patterns, the sediments are divided into two compositional groups. The Type 1 sediments have a REE chemistry similar to the upper continental crust, and have been derived from the > 3.2 Ga composite peninsular gneisses occurring in the low-lying, semi-arid Mysore Plateau. The Type 2 sediments, however, have dominantly intermediate to mafic granulite contributions from the tectonically uplifted Western Ghats, weathered under sub-humid conditions. High concentrations of FeO, TiO 2, Cr and Ni in the sediments suggest mafic-dominated source lithologies in the upper catchment, a feature also confirmed by field observations and petrographic study.

Geochemistry and origin of ferruginous nodules in weathered granodioritic gneisses, Mysore Plateau, Southern India

Fe-nodules occur within saprolites formed from weathering of granodioritic gneisses in the rain-shadow region of the Mysore Plateau adjacent to the Sahyadri Mountains in Southern India. These nodules and their host saprolites were studied for their geochemistry, including chemical speciation, to understand nodule formation and chemical redistribution processes during rock weathering. From their mode of occurrence, and mineralogical and geochemical data, we infer that the nodules originated by a two-stage process in which the initial extensive weathering of gneisses likely facilitated subsequent ferrolysis weathering and nodule formation. Nodules originated by precipitation of goethite, hematite and gibbsite along with several amorphous phases within the matrix of weathered gneisses. This is possible only under hydromorphic conditions, suggesting that parts of the plateau must have gone through a humid phase prior to the present aridity. In the saprolites, Al, Fe, and Ti become enriched because of the removal of Si, Ca, Na, and K. However within the nodule, Fe, Ti, Cr, and Ni are deposited after their chemical transport from the saprolite. Titanium, known for its immobile nature, was also mobilized and concentrated under the conditions of nodule formation. The most important elements in the nodule constitution are Fe, Al, Ti, and Mn, each having both crystalline and amorphous phases. Fe–Ti and Mn oxyhydroxides grain coatings in the saprolites and discrete amorphous Mn and Ti phases in the nodules seem to have scavenged trace elements from the weathering profile. REE were mobilized during weathering and nodule genesis in which Ce and Ti show a strong geochemical coherence. The enrichment of only HREE in saprolite, and both HREE and LREE with significant Ce in the nodule, indicate the control of evolving secondary minerals in the REE redistribution during rock weathering. Strong enrichment of Ce in the weathering profile and in nodules has important implications to the REE chemistry of river waters.

Tectonic stress field in the Indian subcontinent

A map of maximum horizontal compressive stress orientation in the Indian subcontinent has been prepared using orientations derived from three different stress indicators: borehole elongation breakouts, in situ hydraulic fracturing measurements, and earthquake focal mechanisms. Most part of the subcontinent appears to be characterized by a compressional stress regime (thrust and strikeslip faulting) imposed by plate boundary forces although SHmax orientations do not, in general, show clear correlation with the direction of motion of the Indian plate. Four provinces are recognized on the basis of regionally consistent orientations. These are the midcontinent stress province, the southern shield, the Bengal basin, and the Assam wedge. Their boundaries have been determined taking into consideration regional tectonics and seismicity. Central and northern India, including the Shillong Plateau stretching up to the great Himalaya, Pakistan, and Nepal are included in a broad “midcontinent” stress province characterized by NNE‐ENE oriented SHmax. The mean orientation of SHmax in this province is N23°E, subparallel to the direction of compression expected to arise from the net resistive forces at the Himalayan collision zone, suggesting that it is largely determined by the tectonic collision processes. Much of southern India (Mysore plateau and the high‐grade metamorphic terrain south of the plateau) appears to be part of a second stress province characterized by NW oriented SHmax. These appear close to those of the intraplate stress field prevailing in the central Indian Ocean. A third stress province was recognized in the Bengal basin including parts of West Bengal, Tripura, Manipur, and Mizoram in northeastern India and most of Bangladesh. This province extends eastward from the marginal fault in the western margin of the Bengal basin to the Indo‐Burma subduction zone and is bounded on the north by the E‐W striking Dauki fault. SHmax within the sedimentary pile of the Bengal basin is oriented in E‐W direction, while P axes of earthquakes within the basement and the crust beneath the basin and within the subducted slab of the Indian plate beneath the Indo‐Burman ranges generally trend north ‐ N30°E. SHmax orientations within the sedimentary pile of the basin are parallel to the local (approximately E‐W) direction of the convergence of Indian and Burmese plates, suggesting a casual relation to the resistive forces at the subduction zone in the Indo‐Burma region. Interestingly, the stress field in the basement and the crust beneath the Bengal basin and in the subducted slab is similar to the one prevailing in the midcontinent stress province. Assam wedge stress region occupies the northeastern corner of the Indian plate, including Upper Assam, Arunachal Pradesh, and much of Nagaland. This region subducts beneath a sharply bent continental collision boundary consisting of the northeastern limb of the Himalayan and northern limb of the Indo‐Burman fold belts. As a result, the stress field in this province is depth‐differentiated and most likely responsible for the absence of consistent SHmax directions.

MINERALOGY, GENESIS AND CLASSIFICATION OF FERRUGINOUS SOILS OF THE EASTERN MYSORE PLATEAU, INDIA

SummaryThe relationship of geomorphic and climatic history and formation of the ferruginous soils, formed on the acidic Peninsular Gneiss, of the Mysore Plateau, India, is discussed. The profiles studied are found on two different land systems. The soils of the older, fairly smooth landscape are composed of colluvium over truncated laterite profiles, with a gravel layer and a prominent kaolin layer over the weathered rock. These soils show an accumulation of pedogenic haematite grains in the sand fraction and have considerable kaolinite and amorphous ferri‐aluminosilicate minerals in the clays.The soils of the younger, rugged landscape have similar clay mineralogy, but do not have a gravel layer, or haematite grains. The influence of the coarse‐grained parent rock is seen in the large amounts of quartz gravel. The absence of granulation is attributed to lack of accumulation of iron.The soils have been formed in an earlier, more humid climate than prevails today. The original laterite profiles were formed on a plane surface, and subsequent change in climate has led to change in the land forms and dissection. Truncation of the profiles was followed by deposition of red colluvium over the resistant ferruginous layer.These ancient soils do not fit the criteria for Oxisols in the U.S. classification, but fit well in the French system as ‘Sols Ferrallitiques’, subclass ‘fiablement désatures en (B)’. The soil from a low lying area, formed from colluvium under hydromorphic conditions. is classified as‘Vertisols et Paravertisols'.

Isomorphous Substitution of Iron for Aluminium in Some Soil Kaolinites

AbstractClay (&lt;2 μm) and fine silt (2–20 μm) fractions of twenty seven soil samples from eight tropical ferruginous profiles of the Mysore Plateau (India) were analysed for kaolinite by dehydroxylation and selective dissolution. The considerable amounts of iron extracted by the procedure and the closeness of the SiO2/R2O3 molar ratios (2·00–2·18) to the ideal value of 2·00 indicated that iron was a structural constituent of the kaolinites. The calculated unit cell cation composition of the kaolinites showed a substitution of 0·11–0·82 atoms of Fe(III) for Al in every four octahedral sites. The kaolinites in these soils appear to be products of crystallization from weathering solutions.

Rainfall in the Ceded Districts

The districts of Anantapur, Bellary, Cuddapah and Kurnool form the zone known as the "Ceded Districts" in the Madras State. This zone is a typical dry-farming tract. Barring a few pockets of garden-lands, the major portion of the aren under cultivation in these four districts is rainfed. Hence the nature of precipitation decides the success or failure of farming in this tract. The tract is situated between longitude 3º 4 to 16° 25 and latitude 75° 40' to 70° 33' and at an altitude that varies from 500 to 2500 feet. Bellary and Anantapur form the northern and North-Eastern extremity of the Mysore plateau and Kurnool, and. Cuddapah touch the Enst coast districts of Nellore and Guntur.

The Movement of Subsoil Water 1

IN all densely populated areas the water supply is a matter of primary importance, especially where the rainfall is scanty, and where a large proportion of the supply is derived from shallow wells. Dr. W. F. Smeeth, of the Geological Department of Mysore, has prepared a report dealing with this subject, which is based upon observations made during the year 1909, so that it provides rather a basis for further study than a complete discussion of the subject. The Mysore plateau extends over some 29,400 square miles, and is composed almost entirely of gneisses, granites, and crystalline schists, which are more or less decomposed to a depth of from 50 to in some places as much as 100 feet; the upper 50 feet of this forms a reservoir which is fed by the rainfall, and will hold a quantity of water varying with the porosity of the materials, and from it the wells derive their supply. On account of the seasonal character of the rainfall the level of the water-table varies considerably, and from various considerations the author takes a zone of intermittent saturation having a mean depth of 10 feet, and an average porosity of 12 per cent., as representing the average conditions which occur.