File:Squalodon atlanticus (fossil shark-toothed porpoise tooth) (Miocene; Randle Cliff, Maryland, USA).jpg
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Summary
DescriptionSqualodon atlanticus (fossil shark-toothed porpoise tooth) (Miocene; Randle Cliff, Maryland, USA).jpg |
English: Squalodon atlanticus (Leidy, 1856) - fossil shark-toothed porpoise tooth from the Miocene of Maryland, USA.
Mammals are the dominant group of terrestrial vertebrates on Earth today. The group is defined based on a combination of features: endothermic (= warm-blooded), air-breathing, body hair, mother's milk, four-chambered heart, large brain-to-body mass ratio, two teeth generations, differentiated dentition, and a single lower jawbone. Almost all modern mammals have live birth - exceptions are the duck-billed platypus and the echidna, both of which lay eggs. Mammals first appear in the Triassic fossil record - they evolved from the therapsids (mammal-like reptiles). Mammals were mostly small and a minor component of terrestrial ecosystems during the Mesozoic. After the Cretaceous-Tertiary mass extinction at 65 million years ago, the mammals underwent a significant adaptive radiation - most modern mammal groups first appeared during this radiation in the early Cenozoic (Paleocene and Eocene). Three groups of mammals exist in the Holocene - placentals, marsupials, and monotremes. Other groups, now extinct, were present during the Mesozoic. Whales, dolphins, and porpoises are members of Order Cetacea. Cetaceans have intermediate- to very large-sized bodies that are streamlined (cigar-shaped) and have a thick blubber layer for heat insulation purposes. They are evolutionarily derived from terrestrial mammals that had four legs. The former front legs are now flippers. The hind legs are highly reduced and non-functional in whales. The skull is elongated, with one or two blowholes atop the head. The tail is horizontally-oriented, unlike the vertically-oriented caudal fin ("tail") of a fish. Vertical movement of a whale's tail provides propulsion. Whale bodies have a soft outer skin layer with almost no hair - this improves water flow around the body. Whales are famous for being deep and long divers. Sperm whales can dive to over 9,200 feet deep. Northern bottlenose whales can hold their breath for over two hours. Unlike humans, whales have evolved mechanisms for coping with diving diseases such as nitrogen narcosis and decompression sickness. Cetaceans are subdivided into two groups - the mysticete and the odontocete whales. Mysticete whales are the baleen whales - they include the blue whale, finback whale, humpback whale, gray whale, right whale, minke whale, sei whale, etc. The odontocetes are the toothed whales and include the sperm whale, killer whale, dolphins, porpoises, and belugas. Toothed whales have smaller bodies than the baleen whales. They have one blowhole atop the head and have prominent teeth - they feed on fish and squid and other large animals. Classification: Animalia, Chordata, Vertebrata, Mammalia, Artiodactyla, Cetacea, Odontoceti, Squalodontidae Locality: Randle Cliff, Calvert County, Maryland, USA See info. at: wiki.riteme.site/wiki/Squalodon |
Date | |
Source | https://www.flickr.com/photos/jsjgeology/28342868978/ |
Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/28342868978. It was reviewed on 29 August 2023 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
29 August 2023
Items portrayed in this file
depicts
some value
0.01666666666666666666 second
13
14.303 millimetre
image/jpeg
7 April 2018
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Date/Time | Thumbnail | Dimensions | User | Comment | |
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current | 18:26, 29 August 2023 | 1,999 × 1,148 (1.71 MB) | FunkMonk | Uploaded a work by James St. John from https://www.flickr.com/photos/jsjgeology/28342868978/ with UploadWizard |
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Camera manufacturer | Canon |
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Camera model | Canon PowerShot D10 |
Exposure time | 1/60 sec (0.016666666666667) |
F-number | f/13 |
ISO speed rating | 80 |
Date and time of data generation | 15:44, 7 April 2018 |
Lens focal length | 14.303 mm |
Image title | |
Width | 4,000 px |
Height | 3,000 px |
Bits per component |
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Pixel composition | RGB |
Orientation | Normal |
Number of components | 3 |
Horizontal resolution | 180 dpi |
Vertical resolution | 180 dpi |
Software used | Adobe Photoshop Elements 13.0 (Macintosh) |
File change date and time | 23:06, 18 May 2018 |
Y and C positioning | Co-sited |
Exif version | 2.21 |
Date and time of digitizing | 15:44, 7 April 2018 |
Meaning of each component |
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Image compression mode | 3 |
Shutter speed | 5.90625 |
APEX aperture | 7.40625 |
Exposure bias | −0.66666666666667 |
Maximum land aperture | 4.34375 APEX (f/4.51) |
Metering mode | Pattern |
Flash | Flash fired, compulsory flash firing, red-eye reduction mode |
Supported Flashpix version | 1 |
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Focal plane resolution unit | inches |
Sensing method | One-chip color area sensor |
File source | Digital still camera |
Custom image processing | Normal process |
Exposure mode | Manual exposure |
White balance | Auto white balance |
Digital zoom ratio | 1 |
Scene capture type | Portrait |
Lens used | 6.2-18.6 mm |
Date metadata was last modified | 19:06, 18 May 2018 |
Unique ID of original document | 10F806064138789F56656108C347512F |