petromyzon is not a true fish because of: 1: Absences of operculum and airbladder 2: Absences of paired fins and scales 3: Absences of jaw and cranium 4: Absences of gills and median fins.

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petromyzon along with hugfish are not considered as true fish because they are agnathous and they don't have paired fins and scales but have notochord in both adult and larval stage.so both(2&3) are correct because this question is may be exempler.

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absence of jaw n cranium

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2. absence of paired fins and scales because scales are characteristic feature of all the fishes

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3-- they are knwn as fasle bcz they are jaw less

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absense of jaw and ccranium

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Petromyzon is not a true fish because of:
1. Absence of operculum and air bladder:
The first reason why Petromyzon, commonly known as lamprey, is not considered a true fish is the absence of two important features found in most fish species. Fish typically have an operculum, a bony flap that covers and protects the gills, allowing for efficient respiration. Lampreys lack this structure, making their gills more exposed and vulnerable. Additionally, lampreys lack an air bladder, a gas-filled organ that helps fish control buoyancy and maintain their position in the water column. The absence of these features sets lampreys apart from true fish.

2. Absence of paired fins and scales:
Another characteristic that distinguishes lampreys from true fish is the absence of paired fins and scales. Most fish possess paired pectoral and pelvic fins that aid in maneuverability and stability. Lampreys, on the other hand, have only a single dorsal fin and lack other paired fins. Additionally, lampreys lack scales, which are the bony plates that cover the skin of most fish. The absence of these fin structures and scales further differentiates lampreys from true fish.

3. Absence of jaw and cranium:
One significant feature that sets lampreys apart from true fish is the absence of a true jaw and cranium. True fish, such as bony fish, possess a well-developed jaw that allows them to feed on a variety of prey. In contrast, lampreys have a circular, sucker-like mouth that lacks jaws. This adaptation limits their ability to consume a wide range of food sources. Additionally, lampreys lack a proper cranium, the protective bony structure that encloses and supports the brain. Instead, their cranium consists of cartilaginous material, which is less rigid compared to the bony cranium found in true fish.

4. Absence of gills and median fins:
Lastly, lampreys do not possess true gills and median fins. Gills are the respiratory organs responsible for extracting oxygen from water in fish. While lampreys have gill openings, their gills lack the specialized structure found in true fish. Additionally, lampreys lack median fins such as the anal fin and caudal fin, which are important for stability and propulsion in aquatic locomotion. The absence of these respiratory organs and median fins further supports the classification of lampreys as distinct from true fish.

In summary, Petromyzon, or lampreys, are not considered true fish due to the absence of key features such as operculum, air bladder, paired fins, scales, jaws, cranium, gills, and median fins. These distinguishing characteristics set lampreys apart from true fish and highlight their unique adaptations for survival in aquatic environments.

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