page_title: Chitinozoan
section_title: Young graptolites
hierarchical_section_title: Chitinozoan / Relationships / Young graptolites
caption_attribution_description: Potamogeton natans leaf underside with spawn of Lymnaea stagnalis.
context_page_description: Chitinozoa are a taxon of flask-shaped, organic walled marine microfossils produced by an as yet unknown animal. Common from the Ordovician to Devonian periods, the millimetre-scale organisms are abundant in almost all types of marine sediment across the globe. This wide distribution, and their rapid pace of evolution, makes them valuable biostratigraphic markers.
  Their bizarre form has made classification and ecological reconstruction difficult. Since their discovery in 1931, suggestions of protist, plant, and fungal affinities have all been entertained. The organisms have been better understood as improvements in microscopy facilitated the study of their fine structure, and there is mounting evidence to suggest that they represent either the eggs or juvenile stage of a marine animal.
  The ecology of chitinozoa is also open to speculation; some may have floated in the water column, where others may have attached themselves to other organisms. Most species were particular about their living conditions, and tend to be most common in specific paleoenvironments. Their abundance also varied with the seasons.
context_section_description: The graptolites are colonial organic walled fossils which also occurred from the Ordovician to the Devonian; only part of their life cycle is known and it is not clear how they reproduced. It has been suggested that the Chitinozoa may represent the pre-sicula stages of graptolites - the period between the colony's sexual reproduction, and the formation of a new colony. This hypothesis appears to be supported by the co-occurrence of graptolite and chitinozoan fossils, whose abundances appear to mirror one another. The similar chemical composition of the fossils has been seized by both sides of the argument. Proponents suggest that the use of the same chemical framework is an indicator that the two may be related. However, this factor means that situations favouring the preservation of one will also tend to preserve the other - and the preparation techniques used to extract the fossils will also favour or disfavour the two groups equally. Therefore, the apparent co-occurrence of the two fossils may merely be an artifact of their similar composition. The hypothesis struggles to explain the continuing abundance of chitinozoans after the middle Devonian, when graptolites became increasingly rare.
caption: Chitinozoa might represent gastropod egg sacs.
exif: {"Image ImageDescription": "", "Image Make": "RICOH", "Image Model": "Caplio G4", "Image Orientation": "Horizontal (normal)", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image DateTime": "2007:05:26 12:10:10", "Image YCbCrPositioning": "Co-sited", "Image Copyright": "(C) Caplio G4 User", "Image ExifOffset": "312", "Image PrintIM": "[80, 114, 105, 110, 116, 73, 77, 0, 48, 50, 53, 48, 0, 0, 0, 14, 0, 1, 0, 20, ... ]", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "1919", "Thumbnail JPEGInterchangeFormatLength": "5649", "EXIF ExposureTime": "1/48", "EXIF FNumber": "13/5", "EXIF ExposureProgram": "Program Normal", "EXIF ISOSpeedRatings": "125", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2007:05:26 12:10:10", "EXIF DateTimeDigitized": "2007:05:26 12:10:10", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "16/5", "EXIF ApertureValue": "14/5", "EXIF BrightnessValue": "16/5", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "13/5", "EXIF MeteringMode": "Spot", "EXIF LightSource": "Daylight", "EXIF Flash": "Flash did not fire, compulsory flash mode", "EXIF FocalLength": "11/2", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "2048", "EXIF ExifImageLength": "1536", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "1542", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Manual", "EXIF SceneCaptureType": "Standard", "EXIF Sharpness": "Hard"}