Signor-Lipps Effect Back-Extension Estimate
Model a Signor–Lipps unobserved tail under stationary independent Poisson recovery using caller rate exposure/detection; fitted rate uncertainty and correlated sampling are excluded, not a confirmed extinction date.
Description
A last fossil observation can precede a true range endpoint because recovery is incomplete.
A last fossil observation can precede a true range endpoint because recovery is incomplete. A stationary Poisson model assigns a possible unseen tail.1
Model a Signor–Lipps unobserved tail under stationary independent Poisson recovery using caller rate exposure/detection; fitted rate uncertainty and correlated sampling are excluded, not a confirmed extinction date.
When to use Signor-Lipps Effect Back-Extension Estimate
Use this tool to model a Signor–Lipps unobserved tail under stationary independent Poisson recovery using caller rate exposure/detection; fitted rate uncertainty and correlated sampling are excluded, not a confirmed extinction date.
Prepare the fossil measurements or occurrence records and the chosen calibration parameters. Retain the stated coordinate, age and measurement conventions.
How to use Signor-Lipps Effect Back-Extension Estimate and understand its results
- Prepare the fossil measurements or occurrence records and the chosen calibration parameters. Retain the stated coordinate, age and measurement conventions.
- Enter recoveredOccurrences, observedExposureMyr, recoveryProbability, oneSidedConfidence, lastObservedTimeMyr using the field table and calculation rules, then run the tool.
- Read inferredOccurrenceRatePerMyr, observedRecoveryRatePerMyr, modelUnobservedExtensionMyr, modelExtendedEndpointMyr. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| recoveredOccurrences | Recovered occurrences | integer | Required |
| observedExposureMyr | Observed exposure myr | number | Required |
| recoveryProbability | Recovery probability | number | Required |
| oneSidedConfidence | One sided confidence | number | Required |
| lastObservedTimeMyr | Last observed time myr | number | Required |
Use positive integer recoveries, positive exposure and recovery probability in (0,1], with confidence strictly in (0,1). Report observed and detection-adjusted rates; calculate extension from the observed rate and add it on a forward-time axis.2
extension = −ln(1 − confidence)/observed recovery rate Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| inferredOccurrenceRatePerMyr | Inferred occurrence rate per myr | number |
| observedRecoveryRatePerMyr | Observed recovery rate per myr | number |
| modelUnobservedExtensionMyr | Model unobserved extension myr | number |
| modelExtendedEndpointMyr | Model extended endpoint myr | number |
{
"input": {
"recoveredOccurrences": 10,
"observedExposureMyr": 2,
"recoveryProbability": 0.5,
"oneSidedConfidence": 0.5,
"lastObservedTimeMyr": 10
},
"output": {
"inferredOccurrenceRatePerMyr": 10,
"observedRecoveryRatePerMyr": 5,
"modelUnobservedExtensionMyr": 0.13862943611198905,
"modelExtendedEndpointMyr": 10.138629436111989
}
}Limitations and assumptions
Rate uncertainty and correlated sampling are excluded; the endpoint is not a confirmed extinction date.
Numbers and computed results must be finite; overflow produces an error. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use Confidence Interval on Stratigraphic Range Strauss-Sadler: Calculate one-sided Strauss–Sadler endpoint extension assuming independent uniform recovery over the true stratigraphic range; not simultaneous two-endpoint coverage or corrected for heterogeneous collecting. For a complementary task, use Stratigraphic Range Extent: Summarize observed section-position span and endpoint measurement uncertainty, not true taxon duration; positions share a caller increasing chronological/section convention.
Further background: Estimating time of origin from fossil occurrences.
References
-
Estimating time of origin from fossil occurrences — Palaeontologia Electronica
Similar or alternative tools
- Confidence Interval on Stratigraphic Range Strauss-Sadler
Calculate one-sided Strauss–Sadler endpoint extension assuming independent uniform recovery over the true stratigraphic range; not simultaneous two-endpoint coverage or corrected for heterogeneous collecting.
- Stratigraphic Range Extent
Summarize observed section-position span and endpoint measurement uncertainty, not true taxon duration; positions share a caller increasing chronological/section convention.